No, cheap coax is better than a twisted pair, but cheap coax is much more expensive than twisted pair. Consider how much information there is in a hundred channels of analog television: all those channels are being sent through the cable simultaneously.
I'm not expecting all of Slashdot to have gone through an EE E&M course, but some of the things I see in this thread are just off base.
The beauty of transmission line theory is that you can abstract away the wires and conductors into a sort of tube with a particular impedance. RF engineering is all about matching impedances and ensuring efficient power transfer.
100BaseTx uses ~30 MHz signaling. Gigabit is 125MHz. Even cheap coax is good to a gigahertz so with proper RF engineering it'd be no problem to run ethernet over coax. Cat5 is much cheaper than coax, that's all.
Actually, it does work that way. The problem with the approach, though, is the power loss. In the above scheme, you lose half the power at the first match. Then half again at the second match, so overall you come out with a quarter of the input power.
Using baluns lets you transfer power with higher efficiency.
They're similar: they're both transmission lines. One pair = one coax. With impedance matching and balancedunbalanced conversion, it will work. Whether or not it's worth an exercise in RF engineering is a different matter altogether.
Most consumer grade coax is not that great but I'd but I'd bet the frequency characteristics are better than twisted pair. Keep in mind that a single cheap coax can carry hundreds of channels worth of analog video.
The only time Intel has had an inferior CPU design was the P4 era. And the P4 had _high_ power consumption, in part because the new 90nm process had high leakage currents. They got themselves around that problem by making bigger heatsinks.
Yeah, I think the iPad will be attractive to normal folks. It certainly gives a prospective netbook buyer something to think about.
Like you, I don't like closed platforms. The iPad is pretty and would be fun to play with, but I can't see myself getting one until it gets jailbroken.
I'm not sure which time period you're talking about. I am referring to the '80s bubble where, thanks in no small part to the Keiretsu conglomerate structure of the economy, banks did stupid things and could hide their losses with complicated accounting. This period was capped by the meltdown of the property market, upon which Japan entered its "lost decade". Deficit spending on public works through the lost decade was ineffective in getting the economy started again.
But anyway, sure, Japan and China both have some elements of a command economy. But given their respective histories of economic development I'm not willing to say that their economic models are the same.
[Japan's] economic model, the EXACT same model China is using, works really well you are playing catch-up, but tends to fall apart really quickly once you are about equal with your competitors.
It's a stretch to say that Japan's economic model is the same as China's. While Japan did put a lot of resources into helping grow particular markets, it had no Communist public sector. China pursued a path of gradual privatization that is still panning out.
Japan's economy blew up because people kept making bad loans to each other. Why they made bad loans is more due to human nature and Japanese society than anything else.
It doesn't matter for i2s, it's a clocked interface. As long as setup and hold times are met, the data will be valid. Picoseconds aren't going to mess things up when the setup and hold time specs are measured in nanoseconds or more.
It looks like I have access, so I'll summarize the article. This is the May 2004 "Reference Frame" column in Physics Today, written by David Mermin, titled "Could Feynman Have Said This?"
Mermin came across something that ascribed "shut up and calculate" to Feynman, and was somewhat disturbed. Mermin had written in Physics Today (April 1989) that "If I were forced to sum up in one sentence what the Copenhagen interpretation says to me, it would be "Shut up and calculate!" Therefore he was worried that he perhaps had absorbed the quotation from Feynman at some point, and then used it in his article without proper attribution.
So he embarked on a Google search, finding lots of hits having the quotation as Feynman's, and none for Mermin. But then he realized that none of the web material cited any sources or told the "story" of the quotation. So he thinks he may be a victim of the "Matthew effect," from the "tendency always to assign exclusive scientific credit to the most eminent among all the plausible candidates." In other words, somehow the quotation got attached to Feynman, who is well known for his work in QM.
Next Mermin examines whether or not the witticism actually matches Feynman's personality. He concludes that it doesn't; however Feynman's "habitual irreverence" is probably a factor.
In closing, Mermin lays claim to the saying and awaits evidence that Feynman actually said it.
I think it's called a "spherical" torus because the design represents an evolution from a plain torus. You squash a donut into a roughly spherical space. IIRC the advantage of this configuration over a tokamak is that the stability of the plasma is improved. However there is a fundamental trade-off between stability and energy density, so these designs are less likely to be workable sources of fusion energy.
I got my OED1 compact edition for around $60, in very good condition. I'm not willing to pay $300 a year for a dictionary, but then again I'm not an English major.
This would be an interesting homework problem for a digital design class. First, find the single-cycle instruction that will take the longest amount of time. Then, figure out the critical path. Find the logic delay given a particular modern standard cell library.
This means that you can cram more transistors in to the same area of silicon, allowing you to complete more operations per clock cycle.
This is true, but smaller process nodes also produce faster transistors. When you make things on the chip smaller, you have the practical effect of reducing parasitic capacitance in transistors and interconnect. Lower capacitance means a smaller RC time constant (using a first-order model), so logic will work faster. Intel's 45nm process can create an inverter with a delay of less than 5 ps.
Your statements imply that transistors have a fixed speed, and that the only way to improve performance is parallelism. This is false.
Yeah, it's envisioned that there will be a layer of lithium in order to breed tritium. However lithium cannot be the so-called "first wall" material. You would put the lithium behind the first wall.
The history of fusion energy research is marked by concepts that have not worked as their designers anticipated them to. In the first half of the 20th century, they built pinches, only to discover MHD instabilities. They built tokamaks, only to discover more and different kinds of MHD instabilities. They built spheromaks, only to find that the energy density couldn't go high enough. They built pinches of various kinds, only to find that the particle leakage was too high. They built inertial confinement devices, only to find that the ions would lose their energy rapidly.
So you see, I am skeptical that these "new" concepts will be successful anytime soon. Economical generation of fusion energy is a hard problem. I wish the small-scale guys luck, but I'm not holding my breath.
NIF is a weapons program first and foremost. I don't know why they've been trying to sell it to the public lately. Perhaps they're worried about a cut in funding?
You've put your finger on one of the main issues with Laser ICF: repetition rate. Let's say NIF is designed to do one "shot" per day right now. I've heard that a reactor is going to need to do one shot per second for the economics to work out.
Related to that is the construction of the Hohlraum that holds the DT ice and also serves to re-radiate the incoming laser energy as x-rays. A few years ago each one cost a million bucks a pop. With mass production, it's probably possible to reduce the price enough to make things work out economically. And also there's "direct drive" technology that makes the Hohlraum unnecessary.
Anyway, I don't think Laser ICF is that promising in the short term. The supporting technologies just aren't there yet.
As long as you're comparing fusion to fission, you might want to consider the total amount of waste created. Usually we hear about Cobalt-60 in the context of nickel activation of stainless steel reactor vessels. Cobalt-60 isn't long-lived compared to the high-level waste generated by fission; it has a half-life of about 5 years. Just mothball the reactor core for a few decades, as opposed to trucking tons of highly radioactive material out to a vault (that doesn't exist yet) where it's going to have to sit for thousands of years.
Of course, instead of stainless steel, we're supposed to have "advanced materials" someday which will obviate these issues...
I know you're joking, but I'm pretty sure this dude in my plasma physics class took notes in TeX. And this was the sort of class that fills up blackboards several times over the course of the period.
I should mention though that the guy who did this won the University Medal, which is awarded to the top graduating senior at UC Berkeley.
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Well, for 1) I gather that the whole termination thing and the restrictive topology got old real fast.
For 2), um, Infiniband?
Bandwidth is due mostly to loss in the dielectric; noise is a separate issue.
You haven't really defined "better" so I'm not entirely sure what your point is. If by better you mean optimal cost, then I certainly can't disagree.
I still assert that coax will in general support the transport of more information, digital or otherwise. That's my definition of "better".
No, cheap coax is better than a twisted pair, but cheap coax is much more expensive than twisted pair. Consider how much information there is in a hundred channels of analog television: all those channels are being sent through the cable simultaneously.
I'm not expecting all of Slashdot to have gone through an EE E&M course, but some of the things I see in this thread are just off base.
The beauty of transmission line theory is that you can abstract away the wires and conductors into a sort of tube with a particular impedance. RF engineering is all about matching impedances and ensuring efficient power transfer.
http://en.wikipedia.org/wiki/Transmission_line
100BaseTx uses ~30 MHz signaling. Gigabit is 125MHz. Even cheap coax is good to a gigahertz so with proper RF engineering it'd be no problem to run ethernet over coax. Cat5 is much cheaper than coax, that's all.
Actually, it does work that way. The problem with the approach, though, is the power loss. In the above scheme, you lose half the power at the first match. Then half again at the second match, so overall you come out with a quarter of the input power.
Using baluns lets you transfer power with higher efficiency.
They're similar: they're both transmission lines. One pair = one coax. With impedance matching and balancedunbalanced conversion, it will work. Whether or not it's worth an exercise in RF engineering is a different matter altogether.
Most consumer grade coax is not that great but I'd but I'd bet the frequency characteristics are better than twisted pair. Keep in mind that a single cheap coax can carry hundreds of channels worth of analog video.
The only time Intel has had an inferior CPU design was the P4 era. And the P4 had _high_ power consumption, in part because the new 90nm process had high leakage currents. They got themselves around that problem by making bigger heatsinks.
Yeah, I think the iPad will be attractive to normal folks. It certainly gives a prospective netbook buyer something to think about.
Like you, I don't like closed platforms. The iPad is pretty and would be fun to play with, but I can't see myself getting one until it gets jailbroken.
I'm not sure which time period you're talking about. I am referring to the '80s bubble where, thanks in no small part to the Keiretsu conglomerate structure of the economy, banks did stupid things and could hide their losses with complicated accounting. This period was capped by the meltdown of the property market, upon which Japan entered its "lost decade". Deficit spending on public works through the lost decade was ineffective in getting the economy started again.
But anyway, sure, Japan and China both have some elements of a command economy. But given their respective histories of economic development I'm not willing to say that their economic models are the same.
[Japan's] economic model, the EXACT same model China is using, works really well you are playing catch-up, but tends to fall apart really quickly once you are about equal with your competitors.
It's a stretch to say that Japan's economic model is the same as China's. While Japan did put a lot of resources into helping grow particular markets, it had no Communist public sector. China pursued a path of gradual privatization that is still panning out.
Japan's economy blew up because people kept making bad loans to each other. Why they made bad loans is more due to human nature and Japanese society than anything else.
It doesn't matter for i2s, it's a clocked interface. As long as setup and hold times are met, the data will be valid. Picoseconds aren't going to mess things up when the setup and hold time specs are measured in nanoseconds or more.
It looks like I have access, so I'll summarize the article. This is the May 2004 "Reference Frame" column in Physics Today, written by David Mermin, titled "Could Feynman Have Said This?"
Mermin came across something that ascribed "shut up and calculate" to Feynman, and was somewhat disturbed. Mermin had written in Physics Today (April 1989) that "If I were forced to sum up in one sentence what the Copenhagen interpretation says to me, it would be "Shut up and calculate!" Therefore he was worried that he perhaps had absorbed the quotation from Feynman at some point, and then used it in his article without proper attribution.
So he embarked on a Google search, finding lots of hits having the quotation as Feynman's, and none for Mermin. But then he realized that none of the web material cited any sources or told the "story" of the quotation. So he thinks he may be a victim of the "Matthew effect," from the "tendency always to assign exclusive scientific credit to the most eminent among all the plausible candidates." In other words, somehow the quotation got attached to Feynman, who is well known for his work in QM.
Next Mermin examines whether or not the witticism actually matches Feynman's personality. He concludes that it doesn't; however Feynman's "habitual irreverence" is probably a factor.
In closing, Mermin lays claim to the saying and awaits evidence that Feynman actually said it.
I think it's called a "spherical" torus because the design represents an evolution from a plain torus. You squash a donut into a roughly spherical space. IIRC the advantage of this configuration over a tokamak is that the stability of the plasma is improved. However there is a fundamental trade-off between stability and energy density, so these designs are less likely to be workable sources of fusion energy.
I got my OED1 compact edition for around $60, in very good condition. I'm not willing to pay $300 a year for a dictionary, but then again I'm not an English major.
Google is investing in WiMAX, as it's part of the Clear consortium. I dunno if they'll take it that far, but it's not out of the question.
You mean one is charged, right? They both have a magnetic moment.
It's XC3S1000, not XS3C1000. Been working with these parts too long...
This would be an interesting homework problem for a digital design class. First, find the single-cycle instruction that will take the longest amount of time. Then, figure out the critical path. Find the logic delay given a particular modern standard cell library.
This means that you can cram more transistors in to the same area of silicon, allowing you to complete more operations per clock cycle.
This is true, but smaller process nodes also produce faster transistors. When you make things on the chip smaller, you have the practical effect of reducing parasitic capacitance in transistors and interconnect. Lower capacitance means a smaller RC time constant (using a first-order model), so logic will work faster. Intel's 45nm process can create an inverter with a delay of less than 5 ps.
Your statements imply that transistors have a fixed speed, and that the only way to improve performance is parallelism. This is false.
Yeah, it's envisioned that there will be a layer of lithium in order to breed tritium. However lithium cannot be the so-called "first wall" material. You would put the lithium behind the first wall.
The history of fusion energy research is marked by concepts that have not worked as their designers anticipated them to. In the first half of the 20th century, they built pinches, only to discover MHD instabilities. They built tokamaks, only to discover more and different kinds of MHD instabilities. They built spheromaks, only to find that the energy density couldn't go high enough. They built pinches of various kinds, only to find that the particle leakage was too high. They built inertial confinement devices, only to find that the ions would lose their energy rapidly.
So you see, I am skeptical that these "new" concepts will be successful anytime soon. Economical generation of fusion energy is a hard problem. I wish the small-scale guys luck, but I'm not holding my breath.
NIF is a weapons program first and foremost. I don't know why they've been trying to sell it to the public lately. Perhaps they're worried about a cut in funding?
You've put your finger on one of the main issues with Laser ICF: repetition rate. Let's say NIF is designed to do one "shot" per day right now. I've heard that a reactor is going to need to do one shot per second for the economics to work out.
Related to that is the construction of the Hohlraum that holds the DT ice and also serves to re-radiate the incoming laser energy as x-rays. A few years ago each one cost a million bucks a pop. With mass production, it's probably possible to reduce the price enough to make things work out economically. And also there's "direct drive" technology that makes the Hohlraum unnecessary.
Anyway, I don't think Laser ICF is that promising in the short term. The supporting technologies just aren't there yet.
As long as you're comparing fusion to fission, you might want to consider the total amount of waste created. Usually we hear about Cobalt-60 in the context of nickel activation of stainless steel reactor vessels. Cobalt-60 isn't long-lived compared to the high-level waste generated by fission; it has a half-life of about 5 years. Just mothball the reactor core for a few decades, as opposed to trucking tons of highly radioactive material out to a vault (that doesn't exist yet) where it's going to have to sit for thousands of years.
Of course, instead of stainless steel, we're supposed to have "advanced materials" someday which will obviate these issues...
I know you're joking, but I'm pretty sure this dude in my plasma physics class took notes in TeX. And this was the sort of class that fills up blackboards several times over the course of the period.
I should mention though that the guy who did this won the University Medal, which is awarded to the top graduating senior at UC Berkeley.