AMD FX-8350 Linux Performance-Per-Watt

[bug77]

Here's another interesting review: performance per clock. http://hardocp.com/article/2012/10/2...c_overclocking

[mcgreg]

No, it means that if the 8350 would only get 1 watt it can "compute" for 0,276s and the 8150 would only "compute" for 0,266s. So more would be better. But this number alone says nothing because longer "computing" does not generally mean it does more things.

Well, in that case it actually does. Because

The info says, you need 264,3s/297,8s to finish compiling the kernel.
fx 8350@4,6ghz 0,276s / 264,3s = 0,104 % of the kernel finished = 1 watt
fx 8150@4,6ghz 0,266 / 297,8s = 0,089 % of the kernel finished = 1 watt

correct me if I'm wrong

[droste]

I think you got that wrong - that's seconds per watt, and the 8350 is taking _longer_ per watt. This would mean it's worse, not better?

No, it means that if the 8350 would only get 1 watt it can "compute" for 0,276s and the 8150 would only "compute" for 0,266s. So more would be better. But this number alone says nothing because longer "computing" does not generally mean it does more things.

/edit:
The only meaningful number is indeed this:

297,8 * 79,25 = 23601 kJ for the fx 8150 @ 4,6ghz
264,3 * 72,98 = 19288 kJ for the fx 8350 @ 4,6 ghz

[curaga]

-> the calculation is correct but I dont see any sense in it.
shoulnd't it be more like:

fx 8150@4,6ghz: 79,25 / 297,8 = 0,266
fx 8350@4,6ghz: 72,98 / 264,3 = 0,276

=> the fx 8350@4,6ghz gives 3,8% more performance per watt compared to the fx 8150@4,6ghz

I think you got that wrong - that's seconds per watt, and the 8350 is taking _longer_ per watt. This would mean it's worse, not better?

[mcgreg]

Average watt usage of fx 8150 @ 4,6ghz is 297,8
time to compile is 79,25
297,8 / 79,25 = 3,76 - which is correct

Average watt usage of the fx 8350 @ 4,6ghz is 264,3
time to compile is 72,98
264,3 / 72,98 = 3,62

-> the calculation is correct but I dont see any sense in it.
shoulnd't it be more like:

fx 8150@4,6ghz: 79,25 / 297,8 = 0,266
fx 8350@4,6ghz: 72,98 / 264,3 = 0,276

=> the fx 8350@4,6ghz gives 3,8% more performance per watt compared to the fx 8150@4,6ghz


also I'd calculate
297,8 * 79,25 = 23601 kJ for the fx 8150 @ 4,6ghz
264,3 * 72,98 = 19288 kJ for the fx 8350 @ 4,6 ghz

19288 / 23601 = 0,817 .. means that the fx 8350 almost needs 18% less power than the fx 8150 @ 4,6ghz - for compiling the kernel - which is definitely a better job.

correct me if I am wrong of course



mcgreg

[schmalzler]

All those recent tests on FX-8350 had mtune=generic (at least that's what has been written under the config table). So they don't show the real potential (if any). No AVX, no AVX2, no AES, ...
All those gathered numbers don't have any value...

[curaga]

Very curious results, having the older cpu beat the newer one in perf/W in a number of scenarios. And also having lower idle and max power use!

That's a different result from Windows reviews, which is why it's good we have Phoronix around.

[crazycheese]

Very cool testing!

I agree to spice the test with some good Intel rival... However anyone can do this by running the test on own system and submitting. So please, if anyone has Ivy and time do this

--
Very cool CPU indeed! The 20% AMD has talked about do appear in tests!

Also, its scales like godlike so it could be good idea to overclock the CPU for serious tasks and to underclock it for daily tasks. This way the CPU will be as energy efficient as Intel for daily work and can be turned into a beast for serious load. Ofc, one needs to pull 24hr stability test on it, but the possibility to use ECC makes this feature even more tempting.. ))

Btw, 85 Watts idle and 150Watts load for vicera - compare to my Athlon II x4 630 - 90W idle and 140W full load when in stock - 80W idle and 120W when undervolted to 1.2v (runs at stock Hz, rocksolid).
This is great!

[abacaba]

Well it depends how much overvoltage is needed to get 4.6 ghz. If you need less vcore for the older cpu because it oc better then you see this. oc values are never compareable as those are single part specific.

It doesn't matter what voltage is set to run a core, what current does it takes etc. Even clock rate is not important. Only performance (here measured in seconds) and power consumption (in watts) do count. We can multiply time by power and get the number of joules required to do the job (compile kernel) with given setup, and that number will be better for [email protected]

[Kano]

Well it depends how much overvoltage is needed to get 4.6 ghz. If you need less vcore for the older cpu because it oc better then you see this. oc values are never compareable as those are single part specific.