Joules per iteration (power efficiency)
 

I'm curious how my rig compares to others in terms of power efficiency.
- Haswell i5-4690k stock clock, -100mV undervolted
- 2x8GB DDR3-1600 CL 9-9-9-24 at 1.35V
- 80+Gold PSU (BeQuiet E9 400W)

mprime 29.3:
FFT 4096k: 85W/145.15it/s = 586mJ/it
FFT 4480k: 83W/130.50it/s = 636mJ/it

You'll get a lot more efficiency if you upgrade your RAM. Your CPU is memory bandwidth starved. I'd suggest DDR3-2400 minimum, but faster would be better.

You could also underclock to less than 3 GHz and undervolt significantly. Try it and see how your power efficiency improves.

I've tried setting the RAM to 1866 (+16.6%) which required 1.5V instead of 1.35V. The performance increased by 6.8% but power consumption went up by 18%.

Those 6.8% aren't woth the risk for memory corruption from running out of specs I guess. And getting new old DDR3 is just too pricey.

Mark has done a lot of work on under-clocking and under-volting. Power efficiency goes up, you get a better match between CPU and RAM speeds, and the CPU consequently stalls less waiting for RAM.

[QUOTE=heliosh;470662]I've tried setting the RAM to 1866 (+16.6%) which required 1.5V instead of 1.35V. The performance increased by 6.8% but power consumption went up by 18%.

Those 6.8% aren't woth the risk for memory corruption from running out of specs I guess. And getting new old DDR3 is just too pricey.[/QUOTE]

I wouldn't suggest doing anything that requires an overvolt.

But you could try underclocking your CPU and dropping your vcore 0.3 or more. I have a cluster of machines where I did that and saved 25 or 30 watts each.

I'm not that much interested to improve power efficiency. I just wanted to know how it compares to other systems, especially newer ones (Kaby Lake, Coffee Lake, Ryzen)

[QUOTE=heliosh;470681]I'm not that much interested to improve power efficiency. I just wanted to know how it compares to other systems, especially newer ones (Kaby Lake, Coffee Lake, Ryzen)[/QUOTE]

the problem I think it power efficient will be variable. I don't run the software, but as you bring up price of things gets in the way. my electricity bill is about $22 in electricity usage but a base charge of nearly that amount plus taxes at times. running different setups will give different results even on the same chip style.

[QUOTE=heliosh;470681]I'm not that much interested to improve power efficiency. I just wanted to know how it compares to other systems, especially newer ones (Kaby Lake, Coffee Lake, Ryzen)[/QUOTE]
Yeah. You just stumbled into a pool of a particularly hot topic in some parts, here. :smile:

EDIT: Are the 83w and 85w CPU power? I am looking at my i6700 at 4.3GHz, all cores running in one P95 worker, 2400K FFT. HWInfo shows CPU Power between 90 and 103 W. It also shows CPU Package Power as 104W. The latter value varies with CPU load. Would it be counted as part of the calculation of mJ/it? What about the ~5 additional watts which the RAM draws when P95 is running?

What is the conversion between W/xIterations/sec, and mJ/it?
Another edit: OK. I see where the mJ/it comes from. Please disregard the last question.

One more: Using the 103W upper figure for CPU power on a Skylake, and ~2.4 ms/it, I get 417 it/sec, and 249 mJ/it.
Again, in the DC range, 2400K FFT.

[QUOTE=heliosh;470681]I'm not that much interested to improve power efficiency. I just wanted to know how it compares to other systems, especially newer ones (Kaby Lake, Coffee Lake, Ryzen)[/QUOTE]

There isn't much difference between Haswell and Coffee Lake, clock for clock. Haswell was a big bump up over Ivy Bridge.

The improvements since Haswell, at least for mprime, have almost all been in increased memory speed, thus increased memory bandwidth.

Ryzen cores have half the throughput of Haswell cores. But twice the cores will still be bottlenecked by limited memory bandwidth.

The new sweet spot will be the i3-8100 with dual rank, dual channel DDR4-2400, once the cheap motherboards are out.

The Coffee Lake i3 is basically a Kaby Lake die. The i5 and i7 (6 core) on the other hand are manufactured in a new process (14nm++) which is said to be a bit more efficient:

[QUOTE]A third improved process, "14nm++", is set to begin in late 2017 and will further allow for +23-24% higher drive current for 52% less power vs the original 14nm process. [/QUOTE]
[url]https://en.wikichip.org/wiki/14_nm_lithography_process#Intel[/url]

The i5-8400 isn't that much more expensive than the i3-8100.

[QUOTE=heliosh;470690]The Coffee Lake i3 is basically a Kaby Lake die. The i5 and i7 (6 core) on the other hand are manufactured in a new process (14nm++) which is said to be a bit more efficient:


[url]https://en.wikichip.org/wiki/14_nm_lithography_process#Intel[/url]

The i5-8400 isn't that much more expensive than the i3-8100.[/QUOTE]

The i5-8400 is an interesting chip. It has a very low base clock, which is because it can't maintain AVX2/FMA workloads under 65 watts at higher frequencies.

So the i3 gives 4 * 3.6 = 14.4 GHz cores and the i5 gives 6 * 2.8 = 16.8. That extra 17% in CPU throughput probably won't help at all since the memory bandwidth situation still isn't changed. But you've spent a lot more for the CPU. I don't have the parts to actually benchmark throughput either, keep in mind.

If you want to save power, I'd look at the higher clocked parts, like the Coffee Lake i3 equivalent of the i5-6600. These should undervolt better when underclocked.

I don't have any experience with Zen-based processors to suggest one for efficiency.