The point is- the computer has no time to do anything but transfer data and the overhead associated with it, so if you happen to be doing anything other than transferring data, something has to give, so your data transfer speed is lower. Gigabit will max out a 33MHz, 32 bit PCI bus, but can only take up (about) 1/8th of a 133Mhz 64 bit PCI-X bus, but even in that circumstance, you'll come close to maxing out a 1 GHz Xeon, because TCP/IP has so much computational overhead.
Really, my point is that right now, we don't have a standards based high speed interconnect other than Ethernet, and that is quickly running out of steam. I'm vaguely familiar with Myrinet, but it hasn't seemed to have caught on. (I just read that Myrinet isstandards based.)
Even then, those standards you mention are all about clustering, not general purpose networking. Ethernet has really caught on in the 30 or so years it has been around because it has been very adaptable- maybe that adaptability is exactly what is preventing it from progressing further.
Ethernet seems to be reaching the end of its usable capacity- a gigabit ethernet card running at full bore (wire speed) can max out many machines both on bus bandwidth and CPU utilization. Infiniband appears to be the best alternative, but acceptance is so slow, it may never make it. There is a linux effort with Infiniband, but due to the slow acceptance and development of Infiniband, it seems we may never see the combination of good working hardware and a complete software implementation of the standard.
If Ethernet consumes too many resources, and Infiniband is stillborn, what's the next communications medium for networking and clustering?
I design and test the physical side of ethernet for a living, so I think I state with all honesty and some authority that using anything more than cat-5 cable is wasting money. Kinda like buying 94 octane when your car is designed for and runs fine on 87. It has more capacity than you will ever use. Ok, true cat-5 cable may be hard to find, so when I'm saying cat-5, I'm also mean cat5e. I agree with the other posters that fiber is the way to go for a backbone, but copper is quite a bit cheaper, and pretty reasonably priced. According to the Ethernet spec, fiber is actually held to a higher standard in terms of bit-error rate (fiber is 10^-12, where copper gigabit is 10^-10- I'm pretty sure, I have them in spreadsheets to check against, but anyway, fiber is better) On the other hand, on the interfaces I've tested, the BER on maximum loss (copper) cable is usually far better than 10^-10 so that isn't much to worry about.
Be careful if you are thinking about installing fiber for possible use for 10GbE- there are a bunch of standards, and most of them seem to be incompatible with most current types of fiber, such as requirinig very small diameter single-mode fiber. At the moment the 10GbE world appears to be dominated by the long haul guys, not the LAN manufacturers, so cheap connectorization/fiber is not necessarily high on their priority list.
Remember to keep the length under 100m (as it says in the spec) and don't go through a lot of patch panels (since each connector adds loss). If you are going for maximum length, be very careful how you cut and crimp the cable- the more you can maintain the twist in the wire the better, and the more matched each wire in the pair is, the better.
Interesting fact: Since the loss of cat-5 cable is not well defined per unit length, The test cables (for 100Base-TX) are not specified in terms of length, they are specified in terms of loss. The maximum length cable that you test to is not a 100m cable, it is a 10dB loss at 16MHz cable. With good quality (cat5e) cable, that works out to around 135m.
Two reasons- power and refresh- back when 4M sticks were common- the ram was pretty power hungry, if i remember right, it was about 1W/MB (at 5V). Even if that estimate is really high, it would still take a lot of power to keep up a whole drive worth of DRAM. The second reason is that the "D" in DRAM stands for dynamic- it is really just a single capacitor that drains off rather quickly- on the order of milliseconds, generally. You need to have something read the memory cell, and rewrite it. You really want SRAM- or static ram, but that takes 4 transistors/bit of memory, so they tend to be much less space efficient (and more expensive) than DRAM (which only needs 1 transistor/bit). SRAM doesn't need refreshing, and in general, as long as you aren't reading or writing to it, the current draw is really low.
Stay away from 100Mb ethernet- by design, if you have a 100MB link, there is a continuous stream of a pseudo-random code being transmitted by each side, which means, basically, 40mW per port, no matter the activity. 10Mb uses much less frequent link test pulses. You can also go in and remove the LEDs, which are probably unnecessary in your application. If you really want to go hard-core, you can hack your way into the part using the MDIO interface (Similar to I2C) and disable unused ports individually.
The Altima AC205 is an "ultra low power" part that may be used in the hub you want. It is 100Mb, but to use the power hungry 100Mb mode, both sides have to be 100Mb.
If battery conservation is important, stay away from the inverter- a large portion of the power will go away as heat- look into switching power supplies, which can run up to 80-90% efficiency. Look through surplus catalogs and so forth, buying them factory new will probably be prohibitively expensive, but they can be quite reasonable in surplus.
Also, try to stay away from linear power supplies- they also will convert a lot of your precious power to heat.
Running a desktop computer off a 12V system looks to be pretty easy at first, especially when you look at the common voltages (+/- 12, 5, 3.3V) But the problem starts when you look at how much current each one of those voltage rails use, it's pretty amazing- 30, 40 amps is not unusual.
With lower voltage DC supplies, you have high currents for the same amount of power delivered, so you're also going to want to use pretty thick wire to distribute the power around. This will minimize the loss of power to the resistance of the wire.
"Make Room, Make Room" by Harry Harrison, the book that the movie "Soylent Green" was (loosely) based on, is incredibly dystopic- overpopulation, overcrowding, energy shortages, food shortages, food riots, a huge disparity between the rich and the poor. Pretty depressing.
The beginning of the "Cities in Flight" novels by James Blish are pretty dystopic- life on earth gets so bad, they just take the cities and fly away...
I'm running a SS50 right now, and it runs Linux fine- The biggest problem is the video is an SIS part that is not fully supported under linux- they won't release their IP. There is one page that has some details on what it takes to get it going (code and so-forth) but it's not simple- it takes a bit of work.
I like my ss50 a lot- a little pricey for a barebones system, but it is relatively quiet, and has been running without a hitch for a couple weeks now. The only thing I'm really missing at this point is a decent way to monitor the temperature sensors and fan speed under linux- I haven't had much luck with the lm-sensors package.
No, I think you're wrong. 100Mbit is sent over a copper cable at 125MHz, not 200MHz. I think the original poster was right.
I'm not sure what you are disagreeing with, but I'm right. I don't know where you got the 200MHz number from. 100 Mbit has an 8ns symbol clock- or 125 MHz. What I'm absolutely sure about is that it is not modulated, there is no carrier- 100Mbit ethernet is sent as baseband, +1, 0, and -1V signal levels. I look at 100 Mbit and gigabit every day- if you want to know for who, it should be pretty obvious if you look at my web-page.
ummm... no. On ethernet, there is no carrier signal, and the higher the frequency, the worse the propagation though cables, at 100 MHz the primary culprit is skin-effect, as you go higher, the primary source of loss is dielectric losses (like above 1GHz).
Twisted pair is pretty good for transmitting high frequencies, but not great- I've measured cat-5 cable and about 130m of cable gives you about 10dB of loss at 16 MHz. The advantage of cat-5 over coax is that it is much cheaper and easier to terminate. You want to use higher frequency cables because it lets you get faster rise-times on your signal, so you can stuff more signal changes/second.
For 100 Mbit ethernet, the *baud* (symbol) rate is 125 MBaud/s (and hence 125 MHz bandwidth)- it uses an encoding called 4B/5B to encode the clock into the data and only waste about 1/5th of the bandwidth. The *bit* rate is just 100 Mbits/s. 10 Mbit uses a much lossier way of encoding the clock and data, which sends about 20MHz of bandwidth down the wire. Gigabit Ethernet is also 125 Mbaud/s, but each symbol encodes more than one bit (it has 5 level signalling) and 4 channels (pairs) to transmit on. Plus they use 8B/10B encoding. Since it is still 125Mbaud/s, it still is within the same bandwidth as what 100 Mbit uses. It just uses it more efficiently. Of course, you don't get something for nothing, so you lose sensitivity in your reciever. The major gigabit ethernet PHY manufacturers all use DSP cores in their parts to achieve gigabit speeds.
Plenty of people are using PICs, even putting them in new designs (like me- I use them both for play and professionally)- not everything needs the power of a 32 or 64 bit OS. You can get a 12C508 (an 8 pin microcontroller with 0.5K of program space) in quantity for about $0.50USD each! You can make something with a PIC that is extremely reliable- which is exactly what an embedded system is- it's not about being a computer, it's about doing some function. A PIC is maybe a *bit* low powered for doing heavy duty MIDI, since you don't have a lot of time between bits, but people have done it.- check out this site for a bunch of MIDI/PIC related resources.
For general PIC support, there are a couple active mailing lists, the big one is the piclist, and there is a website that will give you plenty of (3rd party) info on the PIC and the mailing list. There is even some GNU/Linux work being done with Linux, try out Gnupic. Of course, you can always go to the manufacturer.
There is a difference- it is used to distinguish between "mass-market" and "trade" paperbacks:
Here is a link.
From that link:
Mass-market paperbacks (pbk)
AKA "rack sized", these are the books that you can find in any store selling books. Most measure aproximately 4.25" x 7".
Trade paperbacks (Tpbk)
Paperbacks that are larger than mass-markets, many times having the same dimensions as a hard cover. Known as trades because they are generally only carried by actual bookstores (in the trade) and not in non-bookstores, like grocery stores. (This however is starting to change.)
I've read just about everything from Joe Haldeman- Forever War is one of his best. Others have mentioned things about the Forever Peace and Forever Free. They are all different novels, but Forever Free was neat and fun, until the very end, which was very disappointing. I'm not going to give it away, but it seems that when he was writing Forever Free, he was going strong and then had to finish it quickly to fulfill some contractual obligation. I didn't go into this book thinking that it would be more of the same, but I do want a good story, not one that makes me wonder why I even bothered reading the book.
I know you want to use your PC, but try to get a real live scope- you'll probably spend less money and get a better measurement device. A sound card would be barely good enough for doing audio measurements, but you run into the problem of an impedance that is too low, with too low a bandwidth. Yeah, you may only want to look at audio frequencies, but realistically, you want a scope with 3-10 times the bandwidth of the highest frequency you'll be looking at.
You don't specify what frequencies you want to work with, but for any sort of digital work I wouldn't suggest that you use *anything* less than a 30 MHz bandwidth analog scope. With that, you'll see a lot of rounding on a 10MHz signal, but you'll be able to see something. Digital scopes are very nice, if they have a decent sample rate. To get the equivalent performance of a 30 MHz analog scope in a digital scope, the digital scope must have at least a 30MHz bandwidth and 100MHz sampling rate (or a good equivalent time setting).
Bandwidth is *very* important. Oscillations can and will happen, and if it is a high frequency parasitic oscillation, a low bandwidth scope will fool you into thinking there is nothing there. You will spend many, many hours trying to debug such a circuit, because your tools will lie.
If you look around (hamfests, ebay) you should be able to find a working old tektronix boat-anchor for between $100 and $200. I've seen plenty of kits available, but they all cost more and have less performance. Since you don't say that you want to build the scope as a learning experience, you want it as a tool. The scope should be your third piece of electronic test equipment, after a multitester and a logic probe. These tools are fundamental. Get something good, whose performance you can trust, that you won't need to debug.
We have no disagreement- you're repeating what I said:
you can't just turn 1 slot into 2 without a bridge built onto the riser
You can also run into the problem of violating the PCI power limits if you try to power 2 cards off of one slot. Most cards don't come near to the limit, but you increase the odds of a problem by trying to power more than one card.
Because of the way PCI works, you can't just turn 1 slot into 2 without a bridge built onto the riser, or a specially modified slot on the motherboard that brings out another PCI REQ/GNT pair. In that case, the PCI riser must be paired with a specific motherboard, since there is no standard for this.
The thing that bugs me most about the selling of information by the government is that too many legislators are looking at government as a business, and not as a public service. Yes, government has to be paid for, but that is why they have the rights to levy taxes. Since so many legislators are pledging to lower taxes to get elected... This is what happens. The government still has functions that it is expected to perform, but no way to pay for them. When we demand lower taxes, we also have to expect reduced services.
Selling public records quickly becomes a conflict of interest, because first and foremost, the primary responsibility of a government is to the residents. When selling things becomes a priority- who wins? Probably the person who is waving the cash, not the resident. The resident forked up cash, but that was way back in April. One thing we have to remember- the government is a non-profit institution. Once it starts making a profit- that's called corruption.
What we're calling public records should be available, but for public safety purposes only, police, hospitals, health departments. I can see circumstances where ownership records should be made available (such as who owns that vacant lot with the toxic waste dump), but those records should at the very least, be prohibited from redistribution (can't we get copyright to work on our side?). Direct marketers will still be able to get names and addresses, they will just have to work a bit harder, and not go to the easiest, cheapest source.
If you're going for complete realism, you need to have at least 15% of your cabinets broken at any time, a surly manager and a handful of early teens that hog the cool games, and can kick your ass in all of them.
On a more functional note- spend some time on lighting- you want to use diffuse, indirect light that won't cast a glare. Most arcades I remember were painted some very dark color inside, and kept pretty dim. Put some padding and carpet down on the floor, a smooth concrete floor (typical of garages) can be really ugly acoustically, especially if you just want to hear the game you're playing. Also, it can be really painful if you are planning on spending a lot of time in front of that game going for the new world record. Acoustic tile on the ceiling would also be good. For the sake of your neighbors, consider some decent soundproofing in the walls.
Be very careful about trying to do too much at once- you can quickly make a system that is just too complex to debug. Try to design in small, testable parts that you have the tools (scope, DVM, etc.) and the knowledge to debug. For this type of design, wire-wrap works great. It lets you try out things easily and make changes quickly. You will get things wrong, you will mis-wire, and so forth. Avoid high speed clocks (>10 MHz) at this point- they can throw all sorts of weird things in your way that are difficult to track down. Stay away from those white plastic proto boards that you can plug wires into- unless you are willing to run with very slow clocks (less than 1MHz), since the parasitic capacitances and leakages can also do very weird, unpredictable things.
I tried to do a similar project a few years ago with a dual-slope A/D converter. A project like this can be very useful in honing your design skills, but it can also very easily frustrate you. This is the project that makes me be very careful about what projects I tackle. You want to learn, but you also need some success in the meantime to keep you going.
For a design like this, something like an FPGA based project is a good idea since there are good simulation tools available, and you can very quickly re-design. Also, this will be a lot closer to what you will be doing in the "professional" world if you do go into digital design. The tools are expensive, but you may be able to get discounts or borrow from your school or the local FPGA rep (Altera and Xilinx are the two that come to mind). They know that once you graduate, you may have infuential power over design decisions, so they will be willing to listen.
I know it's going to be ugly, but the next step is getting an ohmmeter and tracing out the circuit. Another idea- it could be a transistor (mosfet) switch used to switch the power on and off- check to see if any of the traces from the power switch make it there.
If it is a power switch or regulator, it will be connected to the battery/external voltage, and also to the internal voltage. Try to trace these out and see if/where they connect to this part. If you're not an EE/technician or at least have some knowledge of electronics, this reverse engineering could be very hard. Think of it as a way to learn...
If you're very lucky, the fried chip is a voltage regulator that took the brunt of the reverse polarity in a diode designed to be sacrificed for just this sort of abuse. If the destroyed part is not very early in the power supply chain, the prognosis for the rest of the circuit is poor- this may just be the weakest part, other parts may be destroyed as well without visible evidence.
Since the only constraint on this is that it is a 8 pin part, you've got a pretty huge selection of parts to choose from. If you can't get the part identified, your only choice is to trace out the circuit and see how it's hooked up. While there are a great variety of parts out there, many of them are similar or 100% compatible, so by a careful analysis of the circuit, you might be able to identify its function and find a suitable replacement.
Can you take some good close up pictures and make them available?
Is it just a cost issue or is is an availability issue? I think it would be pretty hard to beat $0.18/min with satellite. For a previous job, I took a long trip on a ship and our only internet connection was via Inmarsat (and analog modem)- which, if I remember correctly, was at least $1.00/min.
If you want automatic positioning- check out the satellite antennas that they put on boats- they have 3 axes of gimbal so that they will continue to point at a satellite while the ship is moving at sea- your problem should be a bit easier, since you probably don't need the connection while moving.
Bluetooth does interfere with 802.11- they are both using the same 2.4 GHz band (as a bunch of other things too) but they do interfere- they don't completely knock each other out, but they will degrade each other's range and total throughput. I wish I had a good reference for it- my information comes from a talk I heard from a guy on the Bluetooth committee. That 2.4 GHz band is a free-for-all. Telephones, Bluetooth, 802.11, wireless cameras, and whatever the next big thing is. You only have so much bandwidth, and you have to share.
As a cable to something like a printer- yep, that's the whole idea behind bluetooth- as a way to eliminate wires, and I'm sure we'll be seeing more of it. Eliminating wires is just the beginning- the real amazing stuff will come when things are truly interconnected and it's cheap- cheap really is the selling point behind bluetooth. The manufacturers I've talked to have a goal of about a $5.00 cost for the bluetooth solution. When we get there (802.11 is a more complex solution that is aimed for the higher end, and that is getting pretty cheap- the cards are way under $100, which means that the chipsets are probably under $20). Aside from the irritating marketing potential, having everthing interconnected is the way things are going- where you don't have to worry about synchronizing your Palm Pilot and your phone with your computer, they do it automatically when you're nearby.
Bluetooth has the potential to really change the way computers work with everything- we just have to see if it will really happen. It's not the only thing that we need- and it won't happen tomorrow.
Re:fill the steel columns with water.
on
More WTC News
·
· Score: 2
Corrosion would be a problem, sealing it would be difficult, and if they were one solid column of water, the column at the base would have to be able to withstand about 450 PSI of pressure. Add to this, an impact of a large object would likely crack the column, allowing all the water to leak out at the point of the fire initially (maybe a good thing), but provide no cooling above later- a very bad thing.
Slashdot Mirror
The point is- the computer has no time to do anything but transfer data and the overhead associated with it, so if you happen to be doing anything other than transferring data, something has to give, so your data transfer speed is lower. Gigabit will max out a 33MHz, 32 bit PCI bus, but can only take up (about) 1/8th of a 133Mhz 64 bit PCI-X bus, but even in that circumstance, you'll come close to maxing out a 1 GHz Xeon, because TCP/IP has so much computational overhead.
Really, my point is that right now, we don't have a standards based high speed interconnect other than Ethernet, and that is quickly running out of steam. I'm vaguely familiar with Myrinet, but it hasn't seemed to have caught on. (I just read that Myrinet is standards based.)
Even then, those standards you mention are all about clustering, not general purpose networking. Ethernet has really caught on in the 30 or so years it has been around because it has been very adaptable- maybe that adaptability is exactly what is preventing it from progressing further.
Ethernet seems to be reaching the end of its usable capacity- a gigabit ethernet card running at full bore (wire speed) can max out many machines both on bus bandwidth and CPU utilization. Infiniband appears to be the best alternative, but acceptance is so slow, it may never make it. There is a linux effort with Infiniband, but due to the slow acceptance and development of Infiniband, it seems we may never see the combination of good working hardware and a complete software implementation of the standard.
If Ethernet consumes too many resources, and Infiniband is stillborn, what's the next communications medium for networking and clustering?
I design and test the physical side of ethernet for a living, so I think I state with all honesty and some authority that using anything more than cat-5 cable is wasting money. Kinda like buying 94 octane when your car is designed for and runs fine on 87. It has more capacity than you will ever use. Ok, true cat-5 cable may be hard to find, so when I'm saying cat-5, I'm also mean cat5e. I agree with the other posters that fiber is the way to go for a backbone, but copper is quite a bit cheaper, and pretty reasonably priced. According to the Ethernet spec, fiber is actually held to a higher standard in terms of bit-error rate (fiber is 10^-12, where copper gigabit is 10^-10- I'm pretty sure, I have them in spreadsheets to check against, but anyway, fiber is better) On the other hand, on the interfaces I've tested, the BER on maximum loss (copper) cable is usually far better than 10^-10 so that isn't much to worry about.
Be careful if you are thinking about installing fiber for possible use for 10GbE- there are a bunch of standards, and most of them seem to be incompatible with most current types of fiber, such as requirinig very small diameter single-mode fiber. At the moment the 10GbE world appears to be dominated by the long haul guys, not the LAN manufacturers, so cheap connectorization/fiber is not necessarily high on their priority list.
Remember to keep the length under 100m (as it says in the spec) and don't go through a lot of patch panels (since each connector adds loss). If you are going for maximum length, be very careful how you cut and crimp the cable- the more you can maintain the twist in the wire the better, and the more matched each wire in the pair is, the better.
Interesting fact: Since the loss of cat-5 cable is not well defined per unit length, The test cables (for 100Base-TX) are not specified in terms of length, they are specified in terms of loss. The maximum length cable that you test to is not a 100m cable, it is a 10dB loss at 16MHz cable. With good quality (cat5e) cable, that works out to around 135m.
Two reasons- power and refresh- back when 4M sticks were common- the ram was pretty power hungry, if i remember right, it was about 1W/MB (at 5V). Even if that estimate is really high, it would still take a lot of power to keep up a whole drive worth of DRAM. The second reason is that the "D" in DRAM stands for dynamic- it is really just a single capacitor that drains off rather quickly- on the order of milliseconds, generally. You need to have something read the memory cell, and rewrite it. You really want SRAM- or static ram, but that takes 4 transistors/bit of memory, so they tend to be much less space efficient (and more expensive) than DRAM (which only needs 1 transistor/bit). SRAM doesn't need refreshing, and in general, as long as you aren't reading or writing to it, the current draw is really low.
Stay away from 100Mb ethernet- by design, if you have a 100MB link, there is a continuous stream of a pseudo-random code being transmitted by each side, which means, basically, 40mW per port, no matter the activity. 10Mb uses much less frequent link test pulses. You can also go in and remove the LEDs, which are probably unnecessary in your application. If you really want to go hard-core, you can hack your way into the part using the MDIO interface (Similar to I2C) and disable unused ports individually.
The Altima AC205 is an "ultra low power" part that may be used in the hub you want. It is 100Mb, but to use the power hungry 100Mb mode, both sides have to be 100Mb.
If battery conservation is important, stay away from the inverter- a large portion of the power will go away as heat- look into switching power supplies, which can run up to 80-90% efficiency. Look through surplus catalogs and so forth, buying them factory new will probably be prohibitively expensive, but they can be quite reasonable in surplus.
Also, try to stay away from linear power supplies- they also will convert a lot of your precious power to heat.
Running a desktop computer off a 12V system looks to be pretty easy at first, especially when you look at the common voltages (+/- 12, 5, 3.3V) But the problem starts when you look at how much current each one of those voltage rails use, it's pretty amazing- 30, 40 amps is not unusual.
With lower voltage DC supplies, you have high currents for the same amount of power delivered, so you're also going to want to use pretty thick wire to distribute the power around. This will minimize the loss of power to the resistance of the wire.
"Make Room, Make Room" by Harry Harrison, the book that the movie "Soylent Green" was (loosely) based on, is incredibly dystopic- overpopulation, overcrowding, energy shortages, food shortages, food riots, a huge disparity between the rich and the poor. Pretty depressing.
The beginning of the "Cities in Flight" novels by James Blish are pretty dystopic- life on earth gets so bad, they just take the cities and fly away...
I'm running a SS50 right now, and it runs Linux fine- The biggest problem is the video is an SIS part that is not fully supported under linux- they won't release their IP. There is one page that has some details on what it takes to get it going (code and so-forth) but it's not simple- it takes a bit of work.
I like my ss50 a lot- a little pricey for a barebones system, but it is relatively quiet, and has been running without a hitch for a couple weeks now. The only thing I'm really missing at this point is a decent way to monitor the temperature sensors and fan speed under linux- I haven't had much luck with the lm-sensors package.
No, I think you're wrong. 100Mbit is sent over a copper cable at 125MHz, not 200MHz. I think the original poster was right.
I'm not sure what you are disagreeing with, but I'm right. I don't know where you got the 200MHz number from. 100 Mbit has an 8ns symbol clock- or 125 MHz. What I'm absolutely sure about is that it is not modulated, there is no carrier- 100Mbit ethernet is sent as baseband, +1, 0, and -1V signal levels. I look at 100 Mbit and gigabit every day- if you want to know for who, it should be pretty obvious if you look at my web-page.
ummm... no. On ethernet, there is no carrier signal, and the higher the frequency, the worse the propagation though cables, at 100 MHz the primary culprit is skin-effect, as you go higher, the primary source of loss is dielectric losses (like above 1GHz).
Twisted pair is pretty good for transmitting high frequencies, but not great- I've measured cat-5 cable and about 130m of cable gives you about 10dB of loss at 16 MHz. The advantage of cat-5 over coax is that it is much cheaper and easier to terminate. You want to use higher frequency cables because it lets you get faster rise-times on your signal, so you can stuff more signal changes/second.
For 100 Mbit ethernet, the *baud* (symbol) rate is 125 MBaud/s (and hence 125 MHz bandwidth)- it uses an encoding called 4B/5B to encode the clock into the data and only waste about 1/5th of the bandwidth. The *bit* rate is just 100 Mbits/s. 10 Mbit uses a much lossier way of encoding the clock and data, which sends about 20MHz of bandwidth down the wire. Gigabit Ethernet is also 125 Mbaud/s, but each symbol encodes more than one bit (it has 5 level signalling) and 4 channels (pairs) to transmit on. Plus they use 8B/10B encoding. Since it is still 125Mbaud/s, it still is within the same bandwidth as what 100 Mbit uses. It just uses it more efficiently. Of course, you don't get something for nothing, so you lose sensitivity in your reciever. The major gigabit ethernet PHY manufacturers all use DSP cores in their parts to achieve gigabit speeds.
For general PIC support, there are a couple active mailing lists, the big one is the piclist, and there is a website that will give you plenty of (3rd party) info on the PIC and the mailing list. There is even some GNU/Linux work being done with Linux, try out Gnupic. Of course, you can always go to the manufacturer.
There is a difference- it is used to distinguish between "mass-market" and "trade" paperbacks:
Here is a link.
From that link:
Mass-market paperbacks (pbk)
AKA "rack sized", these are the books that you can find in any store selling books. Most measure aproximately 4.25" x 7".
Trade paperbacks (Tpbk)
Paperbacks that are larger than mass-markets, many times having the same dimensions as a hard cover. Known as trades because they are generally only carried by actual bookstores (in the trade) and not in non-bookstores, like grocery stores. (This however is starting to change.)
I've read just about everything from Joe Haldeman- Forever War is one of his best. Others have mentioned things about the Forever Peace and Forever Free. They are all different novels, but Forever Free was neat and fun, until the very end, which was very disappointing. I'm not going to give it away, but it seems that when he was writing Forever Free, he was going strong and then had to finish it quickly to fulfill some contractual obligation. I didn't go into this book thinking that it would be more of the same, but I do want a good story, not one that makes me wonder why I even bothered reading the book.
I know you want to use your PC, but try to get a real live scope- you'll probably spend less money and get a better measurement device. A sound card would be barely good enough for doing audio measurements, but you run into the problem of an impedance that is too low, with too low a bandwidth. Yeah, you may only want to look at audio frequencies, but realistically, you want a scope with 3-10 times the bandwidth of the highest frequency you'll be looking at.
You don't specify what frequencies you want to work with, but for any sort of digital work I wouldn't suggest that you use *anything* less than a 30 MHz bandwidth analog scope. With that, you'll see a lot of rounding on a 10MHz signal, but you'll be able to see something. Digital scopes are very nice, if they have a decent sample rate. To get the equivalent performance of a 30 MHz analog scope in a digital scope, the digital scope must have at least a 30MHz bandwidth and 100MHz sampling rate (or a good equivalent time setting).
Bandwidth is *very* important. Oscillations can and will happen, and if it is a high frequency parasitic oscillation, a low bandwidth scope will fool you into thinking there is nothing there. You will spend many, many hours trying to debug such a circuit, because your tools will lie.
If you look around (hamfests, ebay) you should be able to find a working old tektronix boat-anchor for between $100 and $200. I've seen plenty of kits available, but they all cost more and have less performance. Since you don't say that you want to build the scope as a learning experience, you want it as a tool. The scope should be your third piece of electronic test equipment, after a multitester and a logic probe. These tools are fundamental. Get something good, whose performance you can trust, that you won't need to debug.
We have no disagreement- you're repeating what I said:
you can't just turn 1 slot into 2 without a bridge built onto the riser
You can also run into the problem of violating the PCI power limits if you try to power 2 cards off of one slot. Most cards don't come near to the limit, but you increase the odds of a problem by trying to power more than one card.
Because of the way PCI works, you can't just turn 1 slot into 2 without a bridge built onto the riser, or a specially modified slot on the motherboard that brings out another PCI REQ/GNT pair. In that case, the PCI riser must be paired with a specific motherboard, since there is no standard for this.
The thing that bugs me most about the selling of information by the government is that too many legislators are looking at government as a business, and not as a public service. Yes, government has to be paid for, but that is why they have the rights to levy taxes. Since so many legislators are pledging to lower taxes to get elected... This is what happens. The government still has functions that it is expected to perform, but no way to pay for them. When we demand lower taxes, we also have to expect reduced services.
Selling public records quickly becomes a conflict of interest, because first and foremost, the primary responsibility of a government is to the residents. When selling things becomes a priority- who wins? Probably the person who is waving the cash, not the resident. The resident forked up cash, but that was way back in April. One thing we have to remember- the government is a non-profit institution. Once it starts making a profit- that's called corruption.
What we're calling public records should be available, but for public safety purposes only, police, hospitals, health departments. I can see circumstances where ownership records should be made available (such as who owns that vacant lot with the toxic waste dump), but those records should at the very least, be prohibited from redistribution (can't we get copyright to work on our side?). Direct marketers will still be able to get names and addresses, they will just have to work a bit harder, and not go to the easiest, cheapest source.
If you're going for complete realism, you need to have at least 15% of your cabinets broken at any time, a surly manager and a handful of early teens that hog the cool games, and can kick your ass in all of them.
On a more functional note- spend some time on lighting- you want to use diffuse, indirect light that won't cast a glare. Most arcades I remember were painted some very dark color inside, and kept pretty dim. Put some padding and carpet down on the floor, a smooth concrete floor (typical of garages) can be really ugly acoustically, especially if you just want to hear the game you're playing. Also, it can be really painful if you are planning on spending a lot of time in front of that game going for the new world record. Acoustic tile on the ceiling would also be good. For the sake of your neighbors, consider some decent soundproofing in the walls.
Be very careful about trying to do too much at once- you can quickly make a system that is just too complex to debug. Try to design in small, testable parts that you have the tools (scope, DVM, etc.) and the knowledge to debug. For this type of design, wire-wrap works great. It lets you try out things easily and make changes quickly. You will get things wrong, you will mis-wire, and so forth. Avoid high speed clocks (>10 MHz) at this point- they can throw all sorts of weird things in your way that are difficult to track down. Stay away from those white plastic proto boards that you can plug wires into- unless you are willing to run with very slow clocks (less than 1MHz), since the parasitic capacitances and leakages can also do very weird, unpredictable things.
I tried to do a similar project a few years ago with a dual-slope A/D converter. A project like this can be very useful in honing your design skills, but it can also very easily frustrate you. This is the project that makes me be very careful about what projects I tackle. You want to learn, but you also need some success in the meantime to keep you going.
For a design like this, something like an FPGA based project is a good idea since there are good simulation tools available, and you can very quickly re-design. Also, this will be a lot closer to what you will be doing in the "professional" world if you do go into digital design. The tools are expensive, but you may be able to get discounts or borrow from your school or the local FPGA rep (Altera and Xilinx are the two that come to mind). They know that once you graduate, you may have infuential power over design decisions, so they will be willing to listen.
I know it's going to be ugly, but the next step is getting an ohmmeter and tracing out the circuit. Another idea- it could be a transistor (mosfet) switch used to switch the power on and off- check to see if any of the traces from the power switch make it there.
If it is a power switch or regulator, it will be connected to the battery/external voltage, and also to the internal voltage. Try to trace these out and see if/where they connect to this part. If you're not an EE/technician or at least have some knowledge of electronics, this reverse engineering could be very hard. Think of it as a way to learn...
If you're very lucky, the fried chip is a voltage regulator that took the brunt of the reverse polarity in a diode designed to be sacrificed for just this sort of abuse. If the destroyed part is not very early in the power supply chain, the prognosis for the rest of the circuit is poor- this may just be the weakest part, other parts may be destroyed as well without visible evidence.
Since the only constraint on this is that it is a 8 pin part, you've got a pretty huge selection of parts to choose from. If you can't get the part identified, your only choice is to trace out the circuit and see how it's hooked up. While there are a great variety of parts out there, many of them are similar or 100% compatible, so by a careful analysis of the circuit, you might be able to identify its function and find a suitable replacement.
Can you take some good close up pictures and make them available?
Is it just a cost issue or is is an availability issue? I think it would be pretty hard to beat $0.18/min with satellite. For a previous job, I took a long trip on a ship and our only internet connection was via Inmarsat (and analog modem)- which, if I remember correctly, was at least $1.00/min.
If you want automatic positioning- check out the satellite antennas that they put on boats- they have 3 axes of gimbal so that they will continue to point at a satellite while the ship is moving at sea- your problem should be a bit easier, since you probably don't need the connection while moving.
Bluetooth does interfere with 802.11- they are both using the same 2.4 GHz band (as a bunch of other things too) but they do interfere- they don't completely knock each other out, but they will degrade each other's range and total throughput. I wish I had a good reference for it- my information comes from a talk I heard from a guy on the Bluetooth committee. That 2.4 GHz band is a free-for-all. Telephones, Bluetooth, 802.11, wireless cameras, and whatever the next big thing is. You only have so much bandwidth, and you have to share.
As a cable to something like a printer- yep, that's the whole idea behind bluetooth- as a way to eliminate wires, and I'm sure we'll be seeing more of it. Eliminating wires is just the beginning- the real amazing stuff will come when things are truly interconnected and it's cheap- cheap really is the selling point behind bluetooth. The manufacturers I've talked to have a goal of about a $5.00 cost for the bluetooth solution. When we get there (802.11 is a more complex solution that is aimed for the higher end, and that is getting pretty cheap- the cards are way under $100, which means that the chipsets are probably under $20). Aside from the irritating marketing potential, having everthing interconnected is the way things are going- where you don't have to worry about synchronizing your Palm Pilot and your phone with your computer, they do it automatically when you're nearby.
Bluetooth has the potential to really change the way computers work with everything- we just have to see if it will really happen. It's not the only thing that we need- and it won't happen tomorrow.
Corrosion would be a problem, sealing it would be difficult, and if they were one solid column of water, the column at the base would have to be able to withstand about 450 PSI of pressure. Add to this, an impact of a large object would likely crack the column, allowing all the water to leak out at the point of the fire initially (maybe a good thing), but provide no cooling above later- a very bad thing.