Stuck at 4GHz with the Phenom II X4 940...
by Gary Key on January 29, 2009 12:16 PM EST- Posted in
- Gary's First Looks
We have been testing the overclocking capabilities of the Phenom II X4 940 (seriously, who names these products?) for an AMD roundup and have hit the proverbial brick wall. It has not been for the lack of trying or even using a stellar motherboard to test these processors. The motherboard choices have ranged from some wicked little 790GX overclockers from ASRock, Gigabyte, and DFI to the flagship 790FX products from ASUS, MSI, and Foxconn. We even tried a few NVIDIA 780a based motherboards along with a slew of newly arrived AM3 compatible boards. We changed cooling, processors, video cards, disk drives, memory, and tried every available voltage setting. It did not matter. We could not break the 4GHz barrier and still complete our benchmark test suite.
The only commonality between our 30 different setups is the operating system. We recently standardized on Vista Ultimate 64 SP1 for testing. Granted, we had this same problem when our 940 engineering samples first arrived and we asked AMD about it. However, AMD never did get to the bottom of it before the launch date. We thought our results might change with retail processors. Alas, they did not. We have four retail CPUs, three with 0850 lot codes and one from the 0849 batch that all behave the same way under Vista 64.
Our final benchmark stable clock speed is 3.955GHz reached via a 17.5 core multiplier and a 226 HTT setting on our . This required a 1.6V VCore setting (with droop, real voltage is around 1.585V) on our DFI DK 790FXB-M2RSH motherboard. Memory speed is DDR2-1205 at 5-5-5-18 timings with VDimm at 2.060V. This is the setting we will utilize in our upcoming roundups. We mention it now as our Core i7 920 will operate at 4GHz and Q9550 at 4.25GHz, not exactly fair, but we are looking at platform capabilities on air cooling in the overclocked sections. As one would say, it what it is.
What is really strange is the behavior of the OS and Phenom II X4 940 at the 4GHz mark. We actually have 3.990GHz (19x210) stable for all tests except Crysis and the PCMark Vantage TV/Movies test suite. With that in mind, a simple change to 19x211 for a 4.009GHz clock speed results in the majority of our tests failing. We sometimes have trouble even entering Vista at 19x211, while 19x210 is about 97% benchmark stable. We have tried every possible combination (20x200, memory at DDR2-800, 1GHz NB speed, etc.) and even chilled the processor down to 16C and raised processor voltages above 1.7, nothing worked above 4GHz.
At least under Vista 64 as Vista 32 was much different. The settings mentioned earlier allowed us to reach a stable 4.275GHz (19x225) with the same components. However, we are not utilizing Vista 32 in testing anymore, especially considering our standard benchmarks are completed with 4GB and 8GB configurations on the DDR2 platforms. As such, it appears at this time that any overclocking comparisons will be limited to under 4GHz on the AM2+ and AM3 platforms. We have addressed this problem with AMD again and hopefully an answer is forthcoming. In the meantime, we figured out a way to get a screenshot above 4GHz before we received the standard BSOD routine. At least it is a consolation prize at this point.
Facebook
Twitter
RSS
48 Comments
View All Comments
Visual - Friday, January 30, 2009 - link
Overreacting much? Jow many cpu samples have you tried with the same result?It seems to me like you just got a bad overclocker or two and are crying foul... but I may be wrong.
If you tried multiple cpus (though I really don't know what number would be ok) from different batches, then I retract my statement. But if you did all this swapping of motherboards, settings and whatnot with the same one or two cpu samples, I think your whole post is completely pointless.
Calin - Friday, January 30, 2009 - link
There were 4 CPUs, three from a batch and one from another, as stated in the article. While 4 CPUs limited at under 4GB in Vista64 and working at 4.25 in Vista32 is nowhere near statistical significant, I think I'll take his opinion as true until/unless I hear otherwise.Holly - Friday, January 30, 2009 - link
Sounds to me like Phenom 2 is having problems running multimedia extension instructions in 64bit mode. Just to note 64bit can quite well use very different instructions (=different parts of cpu). That's about it.Penti - Thursday, January 29, 2009 - link
How about using Phase-change cooling? Not that it wouldn't still get beaten.TA152H - Thursday, January 29, 2009 - link
Have you guys tried it on Windows 7, 64-bit, or Windows XP 64-bit? It could be that Vista is doing something to cause it as is being suggested, or it could be that there are one or more 64-bit instructions that simply can't execute at as high a clock speed, or even a 64-bit register that can't respond quickly enough when overclocked.It is strange that it happens at the 4 GHz threshold, for sure, but it still could be a red herring. It's hard to say without more information, but trying Windows 7, and Windows XP 64-bit would give a little more data to help the analysis.
Griswold - Friday, January 30, 2009 - link
Eh, W7 is essentially Vista under the hood. There wont be any differences, I'm willing to bet real money on that. And XP-64 is just a piece of shit to begin with. If you want to test something truly different that makes sense, do it with a Linux flavour.TA152H - Friday, January 30, 2009 - link
Essentially is an ambiguous term, and there are always changes to "what's under the hood" even from service pack to service pack.I'm not here to judge XP-64 or any operating system, I don't care whether you like it, don't like it, or whatever, it's more about does the processor run on it at higher speeds, regardless of its merits.
Most people buying a processor aren't going to shackle it with Linux, although, for the purposes of identifying where the problem lies, even it could prove useful. The most important consideration is Windows 7, from a practical standpoint, since XP is dying, Linux never lived, and Vista should never have been born. There's no doubt in the near future, most new computers will be running Windows 7, like it or not.
Donkey2008 - Sunday, February 1, 2009 - link
There are thousands of data centers that would probably disagree with your Linux statement.Vista runs perfect on my system. It didn't always do so, but neither did Windows XP for the first 18 months.
Windows 7 = Mohave Experiment. Microsoft changes the interface a little and everybody goes bananas at how great it is.
WillR - Sunday, February 1, 2009 - link
I just ordered a Phenom II 940 yesterday. It's somewhere between NewEgg and me this moment. Oh, and I mention this because I intend to run Linux on it. I also don't intend to overclock it. Just as few people overclock their procs as few run Linux on them.yyrkoon - Thursday, January 29, 2009 - link
Sounds like AMD either did something non standard with their implementation, or somehow Microsoft missed something in their code, or just flat out limited AMD64 somehow. Whatever it is, it sure sounds odd that *only* AMD64 would be affected, in a 64bit environment and I64 was not.