Live data from Hacker News

The Great CPU Stagnation

databasearchitects.blogspot.com

221–222 of 222 posts

Re: The Great CPU Stagnation

#221
post #135

Earlier quoted context omitted.

You're right that the resistance is where the heat is dissipated, but lowering the resistance does not actually change the amount of heat. Transistor switching can be modeled as a step input to an RC circuit [1]. If you integrate the power through the resistor to infinity, you'll see that the value of the resistor drops out. Intuitively, you might think of it like this: to charge a capacitor (or transistor) up to a c…

Ok but again, why do we need the resistors at all? That's what limits the speed at which the capacitor can discharge, so with theoretically 0 resistance you'd get immediate discharge and could go to infinite frequencies, or more realistically as far as the speed of electrons allows for consistent gate switching. To add a bit of troll physics here (but I'm told computers using this sort of principle actually exist), w…

It's not like the resistors are a component that is explicitly added. Every conductor has some resistance - the tiny wires that connect transistors together, the transistor itself, etc. Ideally, yes, you want those resistances to be as low as possible. But in practice there are design trade offs that happen if you do so; it's a balancing act. As the other commenter mentioned, there are no superconducting semiconductors, so the transistor is out. There has been some research into super conductors for the wires, but for the time being there is nothing that's easily integrated into existing manufacturing processes.

Re: channeling electrons - what you've described doesn't quite make sense. Fundamentally, if you're taking an electron at ground or 0V potential, and changing it's potential to VCC, it requires energy that comes from somewhere. The battery (or power supply) is doing exactly that. As the electrons flow back to the ground, the battery "recharges" them up to VCC potential.

What you can do, though, is put circuits in series between supply and ground. That way the electrons flow through the "top" circuit, do their thing, then flow through the "bottom" circuit. There's no free lunch though, as the voltage across each circuit will be reduced. Nonetheless, this is a common technique for low power analog circuits, and one I've used in the past. It's just not practical or worth it in digital circuits like a CPU.

Re: The Great CPU Stagnation

#222
post #50

Earlier quoted context omitted.

I'm pretty sure that when you adjust for inflation, you get more performance per dollar, but I'd need to do math and I don't have the numbers from my head. Does Google Sheets provide a "inflation-adjusted dollar" function?

I’m not sure really. But anyway, I’m not sure if it makes sense to expect performance/$ to always increase anyway. I mean, I know this started out by talking about multicore, but think about single threaded performance. They’ve already grabbed all the low hanging fruit, the challenge now is finding increasingly hard to hunt down tweaks… a small improvement might require massive engineering effort.

Intel may be able to squeeze a little more juice out of x86 by dropping backwards compatibility. This is something I suggested they could have done for Apple because Macs were never supposed to boot MS-DOS anyway.

A simple and regular ISA is what makes ARM easier to implement, which also means lower power because of fewer transistors doing thankless work like decoding instructions and reordering them.

Post reply on HN