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AA affects FSB overclock. Why?

S

scwam

Gawd
Joined
Jul 26, 2005
Messages
829
I've got one of those ccbwe 0530 steppings of the Opteron 170 and it indeed overclocks like crazy. However it has been a real bitch to get my motherboard to stop from crashing until now. Come to find out after several attempts of trying to get the overclock stable for anything over 254x10 has been exhausting. I found out that my 8x AA was causing the crashes. Where before I would last about 1 minute at 265x10 with 8xAA, now I last forever on 270x10 with no AA. Why would this affect my fsb stability??
 
Only thing I can think of is your PSU isn't coping with the load. Your gfx card would draw more power the more work it has to do (8xaa) thus stressing your PSU for power. This might cause your OC to become unstable.

What PSU and gfx card do you have?
 
Yeah, that's sounds like a good possibility. It's a Mad Dog Multimedia Sure Power 450W/500 peak +12v is 20A. I've had it for 11 months and it's been great. Got it for $29 after compusa rebate. my Vcore does vary +/- 0.5 volts, although my brother said that has nothing to do with the psu since it's supplying at least 3volts to the cpu anyway.
I'm running a PNY 6800 GT clocked 416/1300 (420/1350 when it's cold).
 
Do you have a spare PSU you could try? The other thing you could try is putting your gfx card back to stock, then try the CPU overclock again.
 
Don't have another psu. I think I've tried what you mentioned already. Will try it again.
The same instability occurs when using the "Nvidia Performance & Quality Settings" under "Image Settings" tab. If the Image Setting is anything more than "High Performance" it crashes.

The levels are here from lowest to highest

High Performance => Performance => Quality => High Quality
 
20A on the 12v rail is pretty borderline, if that psu can even supply 20a (never heard of a frothing at the mouth dog psu before).

I eliminated my occasional random reboots by getting a good psu, and was able to get a better oc overall.
 
Get yourself a new PSU with at least 26amp on the 12v rail.32-38amp if you can afford it. Good brand name like OCZ,antec,PCpower,enermax,you well be much better off. Kinda surprised its even running half stable with that PSU. :)
 
scwam said:
my brother said that has nothing to do with the psu since it's supplying at least 3volts to the cpu anyway.
Click to expand...


And tell your brother to KNOW what he's talking about before he gives you any more crap advice like this.
 
Same problem again but now with the resolution being set too high. It's as if an increase in texture/resolution/quality whatever increases the chances of a crash. Just off the fly, I based it on this and decided to set my AGP apeture down a notch to 128. This allowed me to increase some of the settings. Decreased AGP aperature again to 64mb and I was able to run at even Higher Quality, with AA, but usually not both at the same time. It allowed me to increase the resolution as well. I stepped the aperature back up to 128 and it decreased my AA/Quality setting limits again. Is this something to do with my load on the memory? Or even having to high of a FSB with too tight timings?

I'm running:

Abit Av8 (k8t800) FSB 280
Opteron 170 @ 2800
2x512mb DDR Corsair Value Ram @ 187 single channel (default is 2.5/3/3/8, set it to 3/3/3/8)
(I can not run more than 2 dimms on this opteron, nor dual channel for some gay reason)
PNY 6800GT (416/1300) (tried at stock settings, made no difference)
LDT = 1 (won't run any other multiplier at this high fsb)
Is it normal for you to have to loosen timing when your FSB gets past 255 as well?
 
Problem on a Via chipset may very well be the AGP/PCI Lock isn't working, so your overclocking the card along with the cpu and not knowing it, add the stress of the AA to the card and crash. Try setting your PCI frequency to 67mhz in the bios to see if it works, but you may not have a functional lock, or it may be a psu, or might just be one of those odd things in teh world.

oh, and your cpu will never recieve more tha 1.7v's or very very bad things will happen.
 
It could also be related to your HTT setting/multiplier. Running AA/AF sends more data across your AGP/PCIe bandwidth, from what I remember about the SLI/SLIx16 benchmarks when they first came out. It may not be able to handle the flood of extra information in its overclocked state, so try dropping the HTT multiplier. (Note, this is just a guess- no guarantees that I'm right, and I may even be talking out of my ass here.)

Otherwise, your power supply definitely sounds like it's a culprit. My Cooler Master RealPower450W (22A split-rail) could hardly handle my old computer's overclock, which was a meager 754 3400+ @ 2.7 with an unlocked 6800 at 400/800. Your Opteron draws a bit more power than my old chip, as does your video card. And my supply had an extra 2A over yours!
 
Hmm, interesting ideas. I can only run the Htt multiplier at 1 at this high fsb. Anything higher it crashes. At 254 it will run at x4 which is slightly over spec. I've read about this agp/pci lock thing, in fact the first av8's that came out did not have a true lock on it. I believe mine does however as I'm not able to even post when I set it to 74mhz lock. I'm testing my memory in single sticks right now. Is it typical for valueram to overclock to 230? This seems quite high.
 
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