I find myself wondering about my perception of this timing business in general. I still think about usecs being fast, but nowadays machines run at lets say 2GHz.
That means that one cycle takes 0.5 nanoseconds. While cycles are easily measurable with the CPU internal cycle counter, I'm still stuck in usec land.
If you wonder how many cycles fit into 5 usec with a 2GHz Processor you find that the OS has 10000 cycles to spare.
While I'm happy that RTLinux is faster than WindowsXP (but not surprised (it says realtime damnit)) I wonder what its doing with all those cycles.
They could just rent a few of those vessels and get through those nasty brownouts they didn't have this year.
This is also not a big political issue as those barges could be pulled away to say Alaska or Mexico when election time comes. One could even put up a long cable and place the ship in international waters - electrical energy out of nowhere.
The paper seems to speak mainly about research based on statistical data. Given that he is epidemiologist this may be relevant to him but it doesn't cover all fields of science equally. So one shouldn't assume that 50% of the math departments papers are wrong, not even the ones about statistics;).
The ABI doesn't matter all that much to you, even if you have to compile code yourself and use the prescribed compiler version. This is important when you are programming assembly, which you have already ruled out with your comment.
You may have figured out by now that ABI means Application Binary Interface (How come you didn't write about it in the article?). As a user you run into trouble mainly when two compilers have to live together on one system, and they support a different ABI.
While all those changes may seem a nuisance to you, this may just be the thing some people are willing to accept to get some benefits out of not having to carry along the remnants of a legacy architecture.
If that's not what you want then Windows may just be the thing for you. To say that Linux developers have failed is maybe a sign of a somewhat overboarding sense of self-importance. Don't forget, that those people frequently write the code for fun or to scratch an itch, if they are happy they certainly haven't failed.
Modern DMA engines frequently allow you to store DMA descriptors in a section of memory usually in the form of a list. You then provide the starting address of the list to the DMA engine, maybe twiddle some bits and of the DMA engine goes and processes the list element by element. The command s in the list can get really fancy depending on the DMA engine. You should read the documentation the article talks about and find out about it, it seems to be a good example of a fancy DMA engine.
This is nice, an article with references, graphs, and formulae. Now this is news for nerds.
Too sad that I'm not too deeply into this. I wonder about their laser performance. The max performance they seemed to get was 8% between diode laser input and output power. Even if they can make improvements I wonder whether this is the right way to get to the 5Kg/KW.
Certainly it would be cool to combine Laserdiodes, which nowadays can get around 50% efficiency and are lightweight, with a secondary laser to get better beamcharacteristics and whatnot. But at 8% that doesn't look good.
Here is a quote out of an interesting document I found with google:
" Passive beam combining/mode control is strongly preferred over active beam combining; passive methods may include, but are not be limited to, spatial filters, grating couplers, phase conjugators, liquid crystals, wavelength couplers, and other transform systems. Materials/coatings development for beam-combining optical components may be proposed if necessary. Performance optimization via modeling is encouraged. The combined beam format should be approximately circular; hexagons and squares are acceptable approximations to a circle; a 1x2 rectangle is not. Diodes yielding a combined diode array bandwidth of £ 50 nm centered at 865 nm or 1040 nm (i.e. atmospheric propagation windows near 1 micron) are required. The defining exit aperture diameter for a 100 kW system should not exceed twelve centimeters. "
It says: Speed: Supersonic Mach 2.5 Range: 10 to 18 miles depending on altitude Length: 9 feet, 5 inches (2.87 meters) Diameter: 5 inches (0.13 meters)
They also have a picture with a hot girl handling one of those.
That gives v=850.72500m/s s=16093.44m t=18s
I should give you some credit in that short an amount of time gut feel says that you won't get through the hull. The sensor is also actively cooled this makes heating up the electronics harder. But I have no clue about this, so my gut is not properly tuned to the problem.
They are talking about a 150kW laser so it could be assumed that it is a continuous laser (this may not be the case though). Even if you would get reflectivity of 90 percent you have to deal with 15kW for a couple of seconds. If you heat 1 kg of Aluminum for 18s with that, your temperature change would be 300K (dead electronics). Of course there is conduction too so you will get less, but don't forget you may have to deal with more heat if reflectivity goes down i.e. 50% -> 1500K (Al melted ~900K ago). (simple math: P*t=c*m*dT)
I think they have a good chance to shoot down your missile with the 150KW laser, with the 15KW prototype laser they may have trouble.
Notice that the ablative system may add weight and decrease range. BTW, the whole laser system decreases missile range, and moves the enemy closer in, or gets the pilot a bit more peace of mind.
There is no good information out there on what kind of laser they are thinking of, any ideas?
I think they spend our money on something interesting. If it fails it will still be a great remote popcorn toasting machine, or an awsome cooling system for that Longhorn running processor could come out of it.
Slashdot Mirror
I find myself wondering about my perception of this timing business in general. I still think about usecs being fast, but nowadays machines run at lets say 2GHz.
That means that one cycle takes 0.5 nanoseconds. While cycles are easily measurable with the CPU internal cycle counter, I'm still stuck in usec land.
If you wonder how many cycles fit into 5 usec with a 2GHz Processor you find that the OS has 10000 cycles to spare.
While I'm happy that RTLinux is faster than WindowsXP (but not surprised (it says realtime damnit)) I wonder what its doing with all those cycles.
They could just rent a few of those vessels and get through those nasty brownouts they didn't have this year.
h tml
This is also not a big political issue as those barges could be pulled away to say Alaska or Mexico when election time comes. One could even put up a long cable and place the ship in international waters - electrical energy out of nowhere.
Oh, barge with something nuclear on it - this reminds me of something:
http://nuclearweaponarchive.org/Usa/Tests/Castle.
Castle Romeo is the first barge shot.
Enough rambling.
Especially from the guy with talking hump syndrome - THS.
Indeed, f???ing would have been more correct.
Damn, this is something only slashdot readers could spell properly.
Well, it takes all kinds.
Now - I'm running OSX and Linux on my Mac, if I were to erase Linux do I have to switch?
Cheers,
have a sip of Pinot Grigio.
The paper seems to speak mainly about research based on statistical data. Given that he is epidemiologist this may be relevant to him but it doesn't cover all fields of science equally. So one shouldn't assume that 50% of the math departments papers are wrong, not even the ones about statistics ;).
The ABI doesn't matter all that much to you, even if you have to compile code yourself and use the prescribed compiler version. This is important when you are programming assembly, which you have already ruled out with your comment.
g 00153.html
In case you actually want to learn something new have a look at this:
http://www.caldera.com/developers/devspecs/
or this to get an overview:
http://www.linuxassembly.org/
You may have figured out by now that ABI means Application Binary Interface (How come you didn't write about it in the article?). As a user you run into trouble mainly when two compilers have to live together on one system, and they support a different ABI.
See here for an example:
http://lists.debian.org/debian-release/2005/04/ms
While all those changes may seem a nuisance to you, this may just be the thing some people are willing to accept to get some benefits out of not having to carry along the remnants of a legacy architecture.
If that's not what you want then Windows may just be the thing for you. To say that Linux developers have failed is maybe a sign of a somewhat overboarding sense of self-importance. Don't forget, that those people frequently write the code for fun or to scratch an itch, if they are happy they certainly haven't failed.
Modern DMA engines frequently allow you to store DMA descriptors in a section of memory usually in the form of a list. You then provide the starting address of the list to the DMA engine, maybe twiddle some bits and of the DMA engine goes and processes the list element by element. The command s in the list can get really fancy depending on the DMA engine. You should read the documentation the article talks about and find out about it, it seems to be a good example of a fancy DMA engine.
Oh and that list is sometimes called chain.
This is nice, an article with references, graphs, and formulae. Now this is news for nerds.
t p%3A//www.fedgrants.gov/EPSData/DOD/Synopses/2181/ BAA05-09/BAA%26%2523032%253B05-09_Sec%26%2523032%2 53B1.doc&ei=2kENQ9WeLaL0-AGP0KHKCQ
Too sad that I'm not too deeply into this. I wonder about their laser performance. The max performance they seemed to get was 8% between diode laser input and output power. Even if they can make improvements I wonder whether this is the right way to get to the 5Kg/KW.
Certainly it would be cool to combine Laserdiodes, which nowadays can get around 50% efficiency and are lightweight, with a secondary laser to get better beamcharacteristics and whatnot. But at 8% that doesn't look good.
Here is a quote out of an interesting document I found with google:
" Passive beam combining/mode control is strongly preferred over active beam combining; passive methods may include, but are not be limited to, spatial filters, grating couplers, phase conjugators, liquid crystals, wavelength couplers, and other transform systems. Materials/coatings development for beam-combining optical components may be proposed if necessary. Performance optimization via modeling is encouraged. The combined beam format should be approximately circular; hexagons and squares are acceptable approximations to a circle; a 1x2 rectangle is not. Diodes yielding a combined diode array bandwidth of £ 50 nm centered at 865 nm or 1040 nm (i.e. atmospheric propagation windows near 1 micron) are required. The defining exit aperture diameter for a 100 kW system should not exceed twelve centimeters. "
http://www.google.com/url?sa=t&ct=res&cd=2&url=ht
Now I wonder why they don't want active combining.
I'm wondering about this, first of all it depends on the range of the missile radar and firing range, lets have an example: http://www.fas.org/man/dod-101/sys/missile/aim-9.h tm
It says:
Speed: Supersonic Mach 2.5
Range: 10 to 18 miles depending on altitude
Length: 9 feet, 5 inches (2.87 meters)
Diameter: 5 inches (0.13 meters)
They also have a picture with a hot girl handling one of those.
That gives v=850.72500m/s s=16093.44m t=18s
I should give you some credit in that short an amount of time gut feel says that you won't get through the hull. The sensor is also actively cooled this makes heating up the electronics harder. But I have no clue about this, so my gut is not properly tuned to the problem.
They are talking about a 150kW laser so it could be assumed that it is a continuous laser (this may not be the case though). Even if you would get reflectivity of 90 percent you have to deal with 15kW for a couple of seconds. If you heat 1 kg of Aluminum for 18s with that, your temperature change would be 300K (dead electronics). Of course there is conduction too so you will get less, but don't forget you may have to deal with more heat if reflectivity goes down i.e. 50% -> 1500K (Al melted ~900K ago). (simple math: P*t=c*m*dT)
I think they have a good chance to shoot down your missile with the 150KW laser, with the 15KW prototype laser they may have trouble.
Notice that the ablative system may add weight and decrease range. BTW, the whole laser system decreases missile range, and moves the enemy closer in, or gets the pilot a bit more peace of mind.
There is no good information out there on what kind of laser they are thinking of, any ideas?
I think they spend our money on something interesting. If it fails it will still be a great remote popcorn toasting machine, or an awsome cooling system for that Longhorn running processor could come out of it.
I understand your plight. DefenseReview wrote about competition to UnderArmor lately. You still have to read the other company's homepage but this is a good direction: http://www.defensereview.com/modules.php?name=News &file=article&sid=710