Thursday, November 05, 2009


I've done a fair amount of testing with my X3 720 Black Edition. My results should be more typical since I'm using the stock heatsink and fan

As I mentioned in my last article people who like Intel's new i5 and i7 processors could argue that the increased wear caused by heat stress doesn't matter because they'll scrap their system in three years anyway. At least, I assume that is what they would say; I haven't heard from anyone who actually uses an i5 or i7 and wants to talk about heat testing with stock HSF. So, it is possible that they are doing better than I have heard. However, with mine I prefer that my system can pass a heavy thermal load test.

I'm currently running:
Phenom II X3 720 Black Edition - 3.4 Ghz; Northbridge - 2.6 Ghz, auto voltage
I cannot hit 3.5 Ghz stable nor can I reach 2.7 Ghz with the NB setting.

OCZ AMD Gold Edition, 7-7-7-19-31, 1333 Mhz, 1.545 volts
To run with these timings I need at least 1.53 volts to be stable.

The standard test program is Prime95. However, this program doesn't give any indication of what is going on with the temperatures so you have to run something else. I ran AMD Overdrive on mine so that I could monitor the temperatures while Prime95 was running. At the very least I would reccomend running the AOD stability test. It is a good test but it doesn't raise the temperature like Prime95. I also tried Intel Burn Test which raises the temperature even more than Prime95 (but not 20 C as the author claims). Mine idles at about 25 C, hits 51 C with Prime95, and reaches 55 C with Intel Burn Test. However, IBT is so buggy that even if your computer crashes it may simply be due to IBT and not due to instability in your system.

For those looking for something simpler I would suggest OCCT 3.1. The regular test on this application heats the same as Prime95 while the Linpack test has heating similar to IBT. However, it also displays core temperatures in real time just like AOD. I would still suggest using a boot CD with MemTest86 to verify the memory. Early on my system would eventually BSOD and reboot even at 3.2 Ghz. So I had wondered if maybe the X3 720 wasn't as good as I had hoped. But, it turned out that the processor was fine and one of my 4 DIMMs was bad. I only confirmed this by running MemTest86. It is also very good at verifying the stability when you change timing or NB speed. I suppose the only thing I haven't tried is using a larger CPU cooler however I wouldn't really expect to get more than maybe 100 Mhz out this. I'm not sure a larger Cooler is really worth it for just 100 Mhz. I'm currently considering getting the new C3 stepping of Phenom II X4 965. With the heat from an extra core a larger HSF might be more worthwhile.

I also tried increasing the Integrated Graphics Processor speed but realistically I don't think you can get much more than 10% this way before your chip gets hot. You might even get 20%. However, I've tried running the free evaluation copy of PassMark's Performance Test and you can really see the graphics bog down. The early tests hit 140 FPS then as the tests get more difficult they go down to 60 FPS, 20 FPS, and 10 FPS. No amount of tweaking of the IGP is going to improve 20 FPS enough to be acceptable, much less 10 FPS. This requires a beefier GPU. So, I'm looking at HD 5770 cards right now. These are pretty close to the older HD 4890 cards so they should be able to handle most graphic loads.

About Intel's i7

So why is it that I seem to be so down on Intel when others think Intel and especially i5/i7 is the greatest thing since sliced bread? Well, I don't have an i5/i7 to test but there are people who do a reasonably good job of testing and don't have a glassy eyed love affair with Intel (like Anand Lal Shimpi). The truth is that Intel's C2D was an excellent processor. However, the initial batch of Kentsfield quads ran hot. In fact, they ran so hot that you could not clock even to 3.0 Ghz without exceeding the rated temperature when using the stock HSF. Ouch. However, the G0 stepping did fix this. And remember that this was at a time when AMD was struggling to hit 2.3 Ghz stock with its own quad core. Then in early 2008 the 45nm Penryns came out and this cut the temperatures even further. The FSB was a serious bottleneck with these quads but again AMD was only creeping up to 2.4 Ghz so it didn't seem to matter. So, Intel enthusiasts had every reason to feel a bit smug. However, by the end of Summer of 2008, AMD was at 2.6 Ghz and using the tweaked 750 southbridge the overclocks were no longer embarrassing. Instead, Intel's severe FSB bottleneck began to be an embarrassment. But, with i7 just around the corner, Intel enthusiasts were able to grin and bear it.

Unfortunately, for i7, it has been a two edged sword. Now that the memory controller is on the die instead of in a separate chip i7 fixes the FSB bottleneck, but i7 also has to handle the entire heat load just as AMD's quad Phenom had to all along. And, just whe i7 was picking up extra heat, AMD had the nerve to release a 45nm Phenom II that actually worked and reduced power draw (just as Penryn did for Intel). Today, heat is once again a serious problem for Intel. But, don't take my word for it. Here at
Benchmark Reviews, Cooling i7 you can see that even undervolted to 1.16 volts, an i7 920 running stock at 2.67 Ghz is 38.5 C over ambient using the stock HSF. So, if your house is 72 F you'll hit 60 C on your processor. Unfortunately, the reviewers were using liquid cooling on both the chipset and video card so most likely your case will be 5 C warmer. In Indiana in the Summer 85 F would not be unsual if you don't have air conditioning. Add 5 C for the case and you are just over the 70 C max that Intel specifies. This is without overclocking. In contrast, my X3 720 running 600 Mhz overclocked would run under 70 C with the same conditions.

Figure in overclocking and it gets far worse. Looking at Benchmark Reviews, i7 Cooling Overclocked we see that running i7 920 at 3.8 Ghz and 1.4 volts increases the temperature by 20 C. With the stock HSF, you would be 10 C over max even at 22 C ambient without a video card. Add in the video card and you are easily 15 C over max. Ouch. But its worse than that. According to the testing, even at 22 C ambient you could easily see 10 C over max even when using a ZeroTherm NV120. A Xigmatek HDT-1S283 or Tuniq Tower 120 will keep you within 70 C just as long as you don't try to push it higher than 3.8 Ghz. And, keep in mind these temperatures are after they laboriously polished the i7's integrated heat spreader to a mirror surface and used a Yate Loon D12SH-12 cooling fan on each product tested. The D12SH-12 cooling fan forces an impressive 88 CFM of air at a moderately noisy 40 dBA. Without these extras your results may be worse.

I know that at this point there will be Intel enthusiasts who will be in full blown denial. They will insist that going over 70 C is nothing and that you can of course go over 1.4 volts and they may even insist that it is impossible for a Phenom II to run cooler since they know that it draws more power. The sad truth though is this quote from the same article:

"The Phenom II processor series from AMD offer a very large 37.31 x 37.31mm (1392.04mm total area) integrated heat-spreader surface, which is the largest processor surface I can recall since the original Intel Pentium (I) days. Compared to Intel's Core 2 Duo and Quad processors which measure 28.5 x 28.5mm, the Phenom II offers over 71% more contact surface area. If you compare the latest Intel Core i7 processors which measure 32 x 35mm, then the Phenom II series offers 24% more contact surface area. For overclockers, this will mean a much larger area to cool, but also much more manageable temperatures."

And, there it is. If you are really committed to Intel and you don't mind spending time polishing the heat spreader and you don't mind the decibel roar of a high volume fan and you don't mind the extra cost of a bolt through kit and you make damn certain that your case is well ventilated then you can indeed get an i7 up to an impressive overclock. Or you could do something similar with a Phenom II with a fraction of the effort because of its 24% larger heat spreader. And, adding insult to injury, AMD just released the C3 Stepping of PII 965 which gives AMD another 100 Mhz bump in overclocking to 4.0 Ghz. Can you match this with an i5 750 or i7 860? Yes, you can but it sure won't be easy. To paraphrase Robert Heinlein, the Intel i7 is a harsh mistress.

1 comment:

Scientia from AMDZone said...

Okay, we'll try unmoderated comments again and see how they work.