3 ms·
Sure, we can all wish that physics were to bend to our 'reasonable' expectations. The reality of it is: 1) increasing the clock rate is hard past 3 GHz or so.
by sliken 8y ago
Sure, we can all wish that physics were to bend to our 'reasonable' expectations.
The reality of it is:
1) increasing the clock rate is hard past 3 GHz or so. The memory wall doesn't get any easier, so IPC drops as clock rate increases. Also heat becomes more of an issue.
2) increasing pipeline length (to make it easier to hit higher clocks) has increasing penalties for each branch misprediction. So IPC drops significantly and you end up back where we are today (high IPC, but low clock).
3) shrinking chips to increase the clock rate no longer works. Generally the insulation layer is so thin that making it thinner results in more leaking.
4) Ever increasingly smart cores (to get higher IPC), makes it ever harder to increase the clock. It's actually pretty amazing what happens in 1/3rd of a ns. Voltage changes in silicon actually move quite slowly (relatively to the speed of light) in silicon. Things like looking at a queue of 80 instructions, figuring out which ones have no pending dependencies, and issuing them to the right unit is pretty impressive for 0.33 ns. Moving to 0.2ns makes it worse.
So could AMD, Intel, or anyone with a decent CPU team design a 5 GHz cpu... sure, no problem. Would it be any faster for general purpose code running on today's 3 GHz CPUs, unlikely.
Personally for my desktop use I don't care about best case performance (0% cache misses), or even average case performance (which is generally way more than I need). I care about worst case performance. Stutters, hangs, lagginess, etc. Linux, enough ram (32GB in my case), GTX 1070, and a M2 for /home. So I welcome the additional cores. Plex transcoding, compressing family videos, making new icons for 10,000 photos, large parallel compiles, etc. Hell sometimes I game while the kids are watching plex streaming and neither of us notice. Thank god for M.2 which killed off the rather serious bottlenecks with SATA.