Overclock Advice

[just1tree]

Ok, so i couldn't take it and not upgrade to a pci-express video card any longer. So i got a A8N32-SLi for the socket 939 platform, with an 8800 gts. Here is my current system components:

A8N32 Sli Deluxe
AMD 4000+ San Diego
EVGA 8800 GTS 320 Superclocked
Scythe Ninja Ultra revision 2 Heatpipe tower
2x512 Kingmax DDR500
HIPER Type R 580W PSU
2x80gig WD raid 0 SATA

So i get the system put together and up and running. Run some stress tests with like oblivion, prime95 etc and things look cool. Temps are good on the cpu, system temps were hot but i found that when i put the fan on the mobo heatpipe that they came down. So i decided to try my hand at oc this bad boy. I was able to get this same cpu to 2.8 on an MSI K8N Neo 2 so i figured that would be my goal here as well. I kinda followed the Anandtech forums quick and dirty isolate/combine process for overclocking and found that my cpu would run prime 95 without errors to 2820 mhz. The mobo would take it's FSB over 330 with the cpu multiplier down to 7, and the memory tested good with memtest to 255.

However, when i went to put a combo of fsb 250 x 11 for a 2750 speed 3dmark 2006 would bomb out on the first test with graphical errors. The computer itself wouldn't crash though. I could escape out of 3dmark and it would just tell me the test was aborted. I tried firing up oblivion, and the same thing happened, tons of grapical errors but not system crashing and returned to desktop ok. Prime 95 ran without errors as well. I kept trying to play with slightly lower values and found that the only speed i could run was 11x235 for a 185 mhz overclock =/

If prime95 doesn't run into any errors, but 3dmark and oblivion crash out what could it be? I was thinking i could try to slow down the memory in case that was the problem, but I don't see how that could be if i could run ok at 10x250 without a problem. I'm certainly dissapointed that i can't get more out of this overclock at the moment to not bottlneck my video card so much. Any ideas or suggestions would be appreciated.

*NB HTT ratio is 4x
*SB HTT ratio is locked at 5x by 200 frequency

i've also tried increasing cpu voltage, but it makes no difference.

thanks for the help.

[Yawgm0th]

Re: Overclock Advice

A CPU overclock causing graphical errors? That's simple: heat or power consumption. The CPU/RAM/Motherboard are increasing the overall system temperature, and this is too much for the video card. Alternatively, they're increasing the power consumption to a point at which problem only occur while using the video card to its fullest extent.

The only other possibility would be a PCI-E bus overclock, and pretty much and competent board will lock the PCI-E bus to 100MHz by default.

I'd set all HyperTransport multipliers to 4x. I don't see how the SB HTT can be locked at 500x200. All HT buses and the CPU frequency are locked to the base clock (which you are currently calling "FSB"), and 250x5 = 1250, which very few boards can do even with increased voltages.

I highly doubt that system is overheating with the cooling you have. Provided you have good airflow, you should only be limited by motherboard and power supply -- which you very well may be. A 580W Hiper is not really ideal for a GeForce 8 socket 939 system with dual Raptors. I'd take a peek at your 12v rail and vcore in a software application while you're running a 3D stress tester.

And for the record, to stress test that, you should run dual Prime 95 instances with each one set to a separate core, using In-Place Large FTTs while having ATITool run it's artifact scan off to the side. ATITool will heat up the card more than most games or 3DMark, and it will even show you a nifty temperature graph, which is highly useful for diagnosing and troubleshooting the source of bad overclocks.

[just1tree]

Re: Overclock Advice

Well this board does have a separate frequency for the 2nd chipset that you can lock outside of the FSB for the SB to NB frequency. And it is supposed to be locked at 200 x5 for a 1000 HTT. I could lower it i suppose as i'm not using the second SLI slot. But i think you might be right about the heat, as my system is housed in a steel chenming case. As i'm righting this, my vga temp is 61 while my cpu is 39. I went back and retried a lower fsb with a higher multiplier yesterday and was able to run 3dmark at 235 x 12 but prime 95 returned errors as soon as the cpu hit 53C. So i retried at 233 x 12 and prime 95 ran for 20 minutes without error this time. My current voltage is 1.49 to cpu, 2.75 to ram, and my +12v rail is stting at 12.10. The PCi express bus is locked at 100 btw, so you were right about that.

Let me know what you think about the chenming case and if it's the problem. Because i have 2 80's in front pulling in cold air, i have a 120 mounted in the side window to bring more cool air for the video and 1 80 in the rear of the case to exhaust (i'd put another 80 in the back for exhaust but the plastic mounting for the other fan is broken =/ ). I read someone in the forums talkinga bout mounting a 120 in the 5.25 cage with zip ties so i did that yesterday to see if that could help air flow to the cpu heatsink and the power supply.

I was looking at the antec 900 because of all the fans it has, but i'm undecided about that particular case, and i want to get a new case purchase right, as this chenming has held up fairly well for me.

[Yawgm0th]

Re: Overclock Advice

61 is definitely high for being in Windows. They usually go between 80 and 100 before you get artifacts, though.

You've got a little too much intake and not enough exhaust, but I don't think airflow is the problem. A temp of 61 while doing nothing 3D indicates to me that the video card doesn't have a good contact with its heatsink or the fan on it's heatsink isn't working properly.

At 12x233, you should be nearly the limits of that processor. You can aways try increasing vcore a little more, but I'd be pretty satisfied with 2.8GHz.