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CallMeDirac
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- TL;DR Summary
- The speed of light is too slow?
I had heard that computer processors are reaching the speed of light. Is this true, and if it is how do we combat this cap?
jim mcnamara said:I am not sure what you mean by 'reaching the speed of light' in processors. Where did you encounter this idea?
As stated, I don't think I could give any kind of meaningful answer.
So to make computers faster, their components must become smaller. At current rates of miniaturization, the behavior of computer components will hit the atomic scale in a few decades. At the atomic scale, the speed at which information can be processed is limited by Heisenberg's uncertainty principle
The signals in a computer travel at close to the speed of light, that will not change.CallMeDirac said:I had heard that computer processors are reaching the speed of light. Is this true, and if it is how do we combat this cap?
I don't agree.anorlunda said:Ever since Moore's Law was proposed in 1965, not a month has gone by without someone predicting that it will come to an end real soon now. So far, they have all been wrong.
The Intel Xeon Phi 7290 processor (now discontinued) can still be found for $8000+, and has 72 cores and a clock rate of 1.5 GHz, with a turbo rate of 1.7 GHz.Vanadium 50 said:The Epyc Rome line tops out at 64 cores and $7000.
The speed of a transistor is mostly due to the relative voltage versus the relative size. For typical chips as seen in home or office computers, as sizes decrease, the density increases, reducing the area available for heat dissipation. In the case of the faster Intel processors, there was a 4 GHz "barrier", dating back to 2012 or 2013 for some Core i7 processors. If not using all cores, then speeds faster than 4 GHz were possible, up to 5 GHz. Liquid cooling allows some processors to run overclocked at up to 8 GHz, but I don't know if these speeds are reliable speeds or just done to set speed records.Mark44 said:... decreasing transistor sizes ... the heat generated increases. To combat the increased heat, CPU vendors have decreased the voltage
Already dealt with, but there's enough confusion in the statement above to warrant some more clarification. When people talk about processor speed, they're talking about the clock rate, which is how fast a particular crystal vibrates, and which has nothing to do with the speed of light. The electrons traveling inside a CPU move at about 1/2 the speed of light ( Computers are becoming faster and faster, but their speed is still limited by the physical restrictions of an electron moving through matter. What technologies are emerging to break through this speed barrier? - Scientific American )CallMeDirac said:I had heard that computer processors are reaching the speed of light.
Again, you are confusing the clock speed with how fast electrons can move through the processor circuitry.CallMeDirac said:And if that speed reaches the speed of light it cannot get faster.
And you are now confusing the speed an EM wave propagates through a dielectric, with the diffusion of electrons through a conductor.Mark44 said:The electrons traveling inside a CPU move at about 1/2 the speed of light...
Yes, that's what I meant -- signals, not electrons. I appreciate the correction.Baluncore said:And you are now confusing the speed an EM wave propagates through a dielectric, with the diffusion of electrons through a conductor.
The signals traveling inside a CPU move at about 1/2 the speed of light...
As far as I know regarding the cores it's not an issue, but for the internal buses (connecting the cores and other parts together) and such, it already is.f95toli said:...latency ... is not(?) yet so much of an issue for the internal processing inside a processor(because they are relatively small)
No, the transmission line will propagate a step and will be impedance matched to prevent ringing.Rive said:I think you need to consider the harmonics of signal edges too.
But it's not simply about transmission, but about having an area where the state changes are in sync (sync enough to have consistent data out of a bus).Baluncore said:the transmission line...
If you transmit the data bits and a register load clock signal, along parallel paths, then the clock will be delayed by the same propagation time as the data. The transfer will be synchronous within itself, but asynchronous with respect to some defined master clock.Rive said:But it's not simply about transmission, but about having an area where the state changes are in sync (sync enough to have consistent data out of a bus).
That's exactly the problem we are discussing. Delay induced asynchronicity between parts of a CPU.Baluncore said:The transfer will be synchronous within itself, but asynchronous with respect to some defined master clock.
Why do the CPU modules need to be globally synchronous?Rive said:That's exactly the problem we are discussing. Delay induced asynchronicity between parts of a CPU.
It's rather 'they cannot be' instead of 'not need to be'.Baluncore said:Why do the CPU modules need to be globally synchronous?
Rive said:latency ... regarding the cores it's not an issue, but for the internal buses (connecting the cores and other parts together) and such, it already is.
That assumes that clock and date lines have the same length. This is even important on a PCB layout - one of my last designs incorporated a DRAM and the guy doing the layout had to measure all lines between the DRAM and the processor and adjust them to be within 1mm of each other. That was in 2005!Baluncore said:If you transmit the data bits and a register load clock signal, along parallel paths, then the clock will be delayed by the same propagation time as the data. The transfer will be synchronous within itself, but asynchronous with respect to some defined master clock.
Svein said:That assumes that clock and date lines have the same length. This is even important on a PCB layout - one of my last designs incorporated a DRAM and the guy doing the layout had to measure all lines between the DRAM and the processor and adjust them to be within 1mm of each other. That was in 2005!
Or that the clock path be very slightly longer in propagation time than any of the data lines.Svein said:That assumes that clock and date lines have the same length.
When a parallel bus was run on a mainframe backpanel, several identical twisted pairs with the same length were used to route the differential signals. Once terminated with wire wrap, the excess length was folded into the gaps between the connector blocks. To modify the back plane required access, carefully unfolding and lifting out the delay lines.ardnog said:We need a delay. Can you just run a wire around the inside of the case?
Good old tech.ardnog said:Can you just run a wire around the inside of the case?
Actually, for this the distance induced delay is not the main player. The structures on the CPU are really small: you can drive them with small effort - you can drive them really fast. But once you are 'outside', you have more capacitance to fill up and more inductivity to stand in the way: the requirements are stricter and so the speed becomes limited.ardnog said:Knowing the size of a motherboard this makes it all too clear how valuable it is to have cache memory located physically on the processor die.
In vacuum, that is correct. On a PCB the speed is closer to 20cm/ns.ardnog said:If I haven't errored the order of magnitude, it looks like light travels 30 cm in one nanosecond,
If you have a relatively new PC motherboard, try to get a glimpse of the traces from the CPU / North bridge to the DRAM. You will see that some of the traces are wiggly - that is due to the fact that they would otherwise be too short relative to the longest traces.ardnog said:We need a delay. Can you just run a wire around the inside of the case?
Rive said:Actually, for this the distance induced delay is not the main player. The structures on the CPU are really small: you can drive them with small effort - you can drive them really fast. But once you are 'outside', you have more capacitance to fill up and more inductivity to stand in the way: the requirements are stricter and so the speed becomes limited.
You need to study transmission lines.ardnog said:Can you recommend me material to read on this?
The maximum speed of processors is constantly evolving as technology advances. Currently, the fastest processors can reach speeds up to 5 GHz.
There is no definitive limit to how fast processors can get. However, as processors get faster, they also generate more heat, which can limit their speed and performance.
Processors are able to reach high speeds through a combination of advanced microarchitecture, increased number of cores, and faster clock speeds.
Yes, the speed of processors can be increased through overclocking, which involves pushing the processor beyond its factory-set speed. However, this can also lead to overheating and potential damage to the processor.
No, the speed of processors is not the only factor that affects performance. Other factors such as cache size, memory, and the type of tasks being performed also play a significant role in overall performance.