Intel i7 and AMD X6 encoding comparision

[LoRd_MuldeR]

Originally Posted by Didée

OT
(Though I wonder a little about Tech ARP's testing methodology for "stock settings": "Please remember to turn off Intel Turbo Tech mode in the BIOS for accurate results with Intel i7 and i5". - In other words: "Make all TurboTech-equipped processors ~5% worse than what they could do at their intended stock settings." If a processor's intended multiplier for all-cores-fully-loaded is multi=(X), they reduce it to multi=(X-1). Don't see why that is "accurate". It would seem more fair to operate a CPU with those spec's which it is designed for to work with.)
/OT

With "Turbo Boost" enabled all benchmark results are less stable, because it's impossible to predict when the CPU enabled the "boost" and when not.

This depends a lot on background process activity. I read the processor rarely uses the maximum boost, because it almost never happens that only one single core is used.

Furthermore it depends on the temperature of the CPU. If the temperature of the CPU fluctuates (which always happens, more or less), then you'll get different benchmarking results.

After all, with Turbo Boost enabled it will be necessary more than ever to take the average from a lot of encoding passes, in order to smooth out outliers.

And x264 shouldn't benefit from Turbo Boost anyway, because Turbo Boost will only become "active" when some of the cores are unused, which won't happen with x264

[STaRGaZeR]

Turbo boost activates when all 4 cores are active too, but the CPU is running below its nominal TDP

[LoRd_MuldeR]

Originally Posted by STaRGaZeR

Turbo boost activates when all 4 cores are active too, but the CPU is running below its nominal TDP

Huh? From what I read, Turbo Boost won't be "activated" until some of the cores fall into the "deep" sleep state (C3).

I also read that Turbo Boost even won't work at all, if those sleeps states are disabled in the BIOS - which obviously is the case with many "all in one" PC's that are sold

EDIT: Okay, it seems that even when all four cores are still active, Turbo Boost can work. But then it will be limited to a "boost" of 266 MHz.

Also it still is uncertain when the CPU stays below its TDP (and thus can increase the clock speed) and when not. This can be different for each encoding process.

Turbo Boost adds a kind of performance fluctuation that wasn't there before. Therefore it will be harder to accurately measure performance with a benchmark...

[STaRGaZeR]

Originally Posted by LoRd_MuldeR

EDIT: Okay, it seems that even when all four cores are still active, Turbo Boost can work. But then it will be limited to one single step of 133 MHz.

True. And unless you run it inside a furnace, it'll permanently run with that extra multiplier, at least here

[LoRd_MuldeR]

Originally Posted by STaRGaZeR

True. And unless you run it inside a furnace, it'll permanently run with that extra multiplier, at least here

Well, this may depend on the cooler that is used, on how good the case is ventilated and even on the ambient air temperature.

If you read the magazines (like German c't magazine), they clearly say that with Turbo Boost enabled there are much greater performance fluctuations than before, which makes obtaining accurate benchmarking results "difficult", if possible at all. So temporarily turning off Turbo Boost for the purpose of benchmarking may make sense indeed.

(Of course with an application like x264, where all four cores are kept at full load and Turbo Boost can only slightly increase the clock speed, the performance fluctuations will be smaller than with a single-threaded application, where Turbo Boost will make a much bigger difference)

[Episodio1]

TurboBoost increases CPU multiplier when one or more cores are at full load.

Depending on application running, if it is single-threaded that particular core frequency will be multiplied by x25 (for example). And when it uses all cores that number would be x22 (when nominal multiplier is x21, for example).

Important issue when benchmarking would be: should we disable turbo boost to do a fair comparison with other CPUs?

[STaRGaZeR]

Originally Posted by LoRd_MuldeR

Well, this may depend on the cooler that is used, on how good the case is ventilated and even on the ambient air temperature.

If you read the magazines (like German c't magazine), they clearly say that with Turbo Boost enabled there are much greater performance fluctuations than before, which makes obtaining accurate benchmarking results "difficult", if possible at all. So temporarily turning off Turbo Boost for the purpose of benchmarking may make sense indeed.

(Of course with an application like x264, where all four cores are kept at full load and Turbo Boost can only slightly increase the clock speed, the performance fluctuations will be smaller than with a single-threaded application, where Turbo Boost will make a much bigger difference)

The best magazine you can read is testing the CPU yourself. Always. Web sites (and magazines even more) are biased and ignorant. Of course temps are crucial, but when you bench you do it in a controlled environment, and if you want consistent results, you get them. You can turn off TB if you want, you'll get accurate results across different tests, but they won't show the true perfomance of the processor. That completely misses the point of benchmarking.

[Atak_Snajpera]

TurboBoost should be disabled during testing because this is nothing but dynamic overclocking.

[CpT]

Originally Posted by Atak_Snajpera

TurboBoost should be disabled during testing because this is nothing but dynamic overclocking.

Exactly...
And tbh 266mhz isn't enough to see any real difference.

[MasterNobody]

Originally Posted by Atak_Snajpera

TurboBoost should be disabled during testing because this is nothing but dynamic overclocking.

But from other hand this official overclocking which is enabled by default (so most users will use it).

[CpT]

So show 2 sets of benchmarks.

One stock clocked, then hard clock to its rated turbo boost speed.

[LoRd_MuldeR]

Originally Posted by STaRGaZeR

The best magazine you can read is testing the CPU yourself. Always. Web sites (and magazines even more) are biased and ignorant. Of course temps are crucial, but when you bench you do it in a controlled environment, and if you want consistent results, you get them. You can turn off TB if you want, you'll get accurate results across different tests, but they won't show the true perfomance of the processor. That completely misses the point of benchmarking.

IMO the proper way would be to first measure the performance without Turbo Boost to get an accurate estimate of the "base" performance, which can be easily compared to other CPU's. Then, on top of that, you can measure the performance on the same processor with Turbo Boost enabled, which gives a (rough) idea of the additional performance gain that Turbo Boost (dynamic overclocking) can reach.

[InsulinJunkie]

Originally Posted by Atak_Snajpera

TurboBoost should be disabled during testing because this is nothing but dynamic overclocking.

Also, don't forget that AMD added their version, "TurboCore", beginning with the X6s, so really it's something we're going to be dealing with from all new CPUs from here on out.

[STaRGaZeR]

Originally Posted by LoRd_MuldeR

IMO the proper way would be to first measure the performance without Turbo Boost to get an accurate estimate of the "base" performance, which can be easily compared to other CPU's. Then, on top of that, you can measure the performance on the same processor with Turbo Boost enabled, which gives a (rough) idea of the additional performance gain that Turbo Boost (dynamic overclocking) can reach.

The problem here is that there's no "proper way", there's just the way you want to do it.

[Didée]

(Ooop's ... after 30 seconds I decided to delete the post because of OT'ness ... but too late, Lord_Mulder was fast and caught me.)

Minor fact: yes, the Nehalems *always* use turbotech when there's sufficient load. The minimum boost is multiplier+1 (i7-750, i7-860) or even +2 (i7-870/875k). The usage of additional turbostates during partial load depends on whether C-State usage is activated in the BIOS, i.e. the higher multipliers are used only while other cores are in sleep state.

But, that "minimum" turbo is used practically *always* when there is sufficient load.

Of course the whole thing can be rated as "overclocking", but after all, it is the way that the processor is meant to work, this is what it has been designed for. My point of view is that it makes sense to operate a CPU in the way it is meant to operate.
In numbers, an i7-750/860 will work at least at multi=21/22 with true stock settings. Disabling turbo, they'll work at 20/21. Now, 21/20 is 1.05, 22/21 is 1.0476. Hence, 750/860 get a penalty of almost 5%. Worse for 870/875k, for which it's 24/22 ~> 9% penalty.

I can't help, but in a competence where some minor differences separate the good from the better from the best, it is not trivial to introduce a penalty of 5% or 9%. That's not peanuts, but some serious performance.


Also, the argument about "repeatabiliy"/"reliability"/" you never know if it kicks in or not" etc.etc. is mostly BS. I've done my tests too, and under same conditions, the repeatability of results is quite good, absolutely in range of normal measuring differences. When you're doing a performance measurement, surely you'll make sure that there are no "big" tasks running in the background. (Nobody measures x264 performance while prim'ing, linx'ing or folding in the background.) And when Windows happens to start a full system backup in the background, then your numbers are screwed anyway, no matter turbo or not-turbo.

Lastly, I (partly) doubt TechARP's numbers for stock settings in yet another aspect. i7-750 almost same performance as i7-860 - On stock settings? Seems that Hyperthreading also has been disabled, for an "even fairer" result?


Next step would be to disable all CPU caches. It is unfair that different CPUs have different cache sizes.

[xlazom00]

can we go back to comparison of x264 fps on i7 and X6 on one thread

We can overclock processors to compare on different frequency.

But we still don't get results to compare.

[Groucho2004]

Originally Posted by xlazom00

can we go back to comparison of x264 fps on i7 and X6 on one thread

Could you explain why this is useful for you?

[Didée]

Originally Posted by xlazom00

can we go back to comparison of x264 fps on i7 and X6 on one thread

We can overclock processors to compare on different frequency.

But we still don't get results to compare.

For real-world usage, look at the graph that Dark Shikari put in post#4. Seems like some serious numbers.

For performance with exclusively-one-thread ... well, it's both possible and valid to compare if a Mercedes or a BMW is faster when only using the 1st gear. But that's not what matters in practice.

Moreover, even when you have the "raw performance" on "only one thread", that doesn't mean that you could just multiply that performance {times cores} or {times threads}. Hence, the significance of single-threaded performance is somewhat limited. When you want to know what a CPU can deliver at max, then you need to load it to max.

[xlazom00]

As I said on first page

I want to compare real speed of i7 and X6 (single core) on x264
single core thread speed get real information about processor speed.

From my experience x264 can't get 100% of full 6 cores on X6 and i7.
At least I can't get it on 1th pass

[Groucho2004]

Here are more recent results from Techarp (2nd pass):
http://www.techarp.com/showarticle.a...tno=669&pgno=2