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CPU limit reached?

M

MDme

Senior member
I'm trying to overclock my A64 3000+ (newcastle) and my present OC is 2.55Ghz (255x10 1:1) and I have the processor at 1.55v. I tried at 2.6Ghz (260x10) but it's not stable at prime95 and I found that the memory is at issue coz i tried a lower multiplier and it still didn't become stable. I tried a ram divider and it worked at 2.6 and 2.65 but both still weren't stable at prime95 (at 1.6 vcore). have i reached the CPU limit? any suggestions on how it can be improved?
 
I've already tried raising vcore to 1.65 and vdimm to 2.8 and it's still not stable. sorry for not stating this earlier.
 
2.8 vdimm may not be high enough do a volt mod or see if the OCZ memory booster is compatible with your motherboard. That may help. What are you using to cool? Air/water/phase change. You may simply have reaching your thermal limits
 
i've monitored my temps and they are 40+ at idle and 61 at full load. i don't really think it's a temp issue at these temps. I am only using retail cooling though. Yeah i do think it's swell that I can reach 2.55Ghz at 1:1 performance rocks!!! you think i can still get over or at least at 2.6?
 
yup. the ballistix memory can do 2.5-2-2-10 or 2.5-2-2-5 at DDR510+. I even have it only at 2.7. Anandtech has the review.
 
Nice then...

Did you try higher timmings to withdraw ram from the list of possible responsible ?
I would guess that cpu has reached it's even point.
 
I didn't try that. Since according to AT the ballistix memory modules do not respond well to higher timings. i.e. increasing timings doesn't improve overclockability. AT said they behave similar to OCZ 3500/3700EB chips. I don't know if I am wrong but I've tried using a ratio for the FSB to run the memory slower than FSB but this didn't stabilize my set-up at 2.6 and 2.65 Ghz (RAM was running around 420 - 450 MHz at those speeds). Doesn't this eliminate the RAM from the equation?
 
I have a 3200+ that seems to hit a wall at about the same speed. It will post at 2.63ghz at 1.71v, but is only prime stable at 2.55ghz (255x10 at 1:1 memory). It will do 2.45ghz at stock vcore of 1.5v (not totally stable though). Cooling is not an issue as I am watercooled and my temps are about 15C better than the OEM air cooler at idle. I am going to do the vcore volt mod and see if I can get to 2.6ghz stable as soon as my OCZ DDR Booster shows up. My OCZ EB will do 260 memtest stable with 3-2-2 timings at 3.0v, but this board undervolts the vdimm slightly with 2.88v when set to 2.9v.

One thing to look into is how your voltage rails look. Mine took a serious beating with my Thermaltake 480W with the 12v rail dipping down to 11.5v under load before upgrading to my new OCZ Powerstream which is rock solid at 12v no matter what I do.
 
That's terrible that you can only get an extra 500something plus out of your 3000+ cpu.
I think you should just sell the setup to me and start over 😉
 
Mine actually is usable at 2.65 Ghz with a DDR clock of approx 450Mhz. It's just not able to last more than a few minutes at prime95 (temps stable at 61-62) it is playable but I don't want to continue this way if it is unstable with prime95 since I've heard that if it's unstable with prime95 it WILL be unstable. I haven't tried 2.7 Ghz though 🙂
 
also I've tried looking at the power rails...i don't see a significant drop in any of the rails. I am using an Antec TruePower 380w PSU and my 12v rail never drops below 11.85 i don't know if that's an issue though.
 
I just purchased the same CPU, motherboard and ram as you and I can't get my memory stable over 207 FSB. It doesn't seem to matter what timings or voltage I run it at. So I'm running my HT at 248mhz and using a 5:6 memory multiplier.. seems to be the limit for me.
 
Seems like a very nice overclock, especially considering that you are only using stock cooling. 61-62C is pretty hot... maybe if you bought a decent HSF you could push another 100MHz out of your CPU? Don't take my word for it though, because your CPU might have already reached it's limit. 2.55GHz is still a very nice overclock. It would be interesting to see how far you can take it on some decent air cooling or even water cooling though 🙂
 
Thanks for the input guys. I'll consider a better fan maybe. I am not too keen on opening the CPU/Heatsink again just to place AS5 but i may try a better fan.
 
Do you have to lower the HTT speed when you OC the fsb that much? I thought you did so it stays around the max the board supports (800 or 1000 depending on board)...
 
Yup, on A64/NF3 you can safely lower the HTT down to 700 with no real performance impact. Nothing that I've noticed, anyway.
 
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