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Cannot Get this CPU Stable

post #1 of 5
Thread Starter 
Hello everyone. This post really consists of two questions.

Recently, I purchased a very nicely priced Phenom II x3 720 BE from eBay, and built a small system around it with some parts I had lying around. When the received this CPU, the first thing I did was attempt to unlock the 4th core. Well, I was not successful, so I turned to overclocking it as far as I could on the air cooler I bought for it (standard air for a FX-8350). The farthest I have pushed this chip is 3.5GHz, and beyond that the machine will not remain stable no matter how much voltage I push. I started playing with ACC, trying to maybe squeeze another 200Mhz or so out of the chip, and the 4th core suddenly appeared. Now, here's my problem: The 4th core is stable at various ACC settings at various clockspeeds no higher than 3.5Ghz. The entire system can take a full 100% processing load for hours:mad:. Prime95 will crash this PC within minutes but that is due to finicky RAM, which I know for sure because when I removed it, suddenly everything was fine. But when I'm not stress testing, no matter which Windows OS I use, 7, 8, 10; I get a BSOD during normal usage with the cause identified as SYSTEM_SERVICE_EXCEPTION. If I disable the 4th core, everything is fine.

So....how can this core (which is weaker than the others for SURE) take a 100% load for hours with no issue, but cause BSODs during normal usage? Temps don't seem to be an issue; and lower clockspeed seems to help; but it won't prevent the BSODs. Does anyone more experienced than I have any ideas as to how I can stabilize this 4th core for normal usage?

P.S. I have enabled this core AFTER a fresh install, and before. Neither has had an effect on its behavior. Thank you for your time.
post #2 of 5
Well now you know why they shut that core off.....

In most cases, these chips would unlock but suffer a lot of voltage increase for stability, not for testing perhaps, but just in general.

So two choices for your question/s

A. Run as a tri-core as intended

B. Try a much lower frequency with all cores. Like 3ghz maybe less??

Quick story shot....

Had a 565BE that unlocked to all four cores. I had hammered hard on that chip killing one of the unlockable cores for good around some 4600mhz and a bit more than 1.65v. Had a major blue screen and it locked up, hard reset and the core never worked again. But that cpu on only two cores as intended hammered along daily at 4.4ghz 1.650v. It was a nice chip. Topped out around 5300mhz on DICE.

I miss unlocking chips.
post #3 of 5
You mentioned everything appeared fine after removing RAM, have you tried raising CPU-NB voltage?
post #4 of 5
Thread Starter 
Quote:
Originally Posted by ShrimpBrime View Post

Well now you know why they shut that core off.....

In most cases, these chips would unlock but suffer a lot of voltage increase for stability, not for testing perhaps, but just in general.

So two choices for your question/s

A. Run as a tri-core as intended

B. Try a much lower frequency with all cores. Like 3ghz maybe less??

Quick story shot....

Had a 565BE that unlocked to all four cores. I had hammered hard on that chip killing one of the unlockable cores for good around some 4600mhz and a bit more than 1.65v. Had a major blue screen and it locked up, hard reset and the core never worked again. But that cpu on only two cores as intended hammered along daily at 4.4ghz 1.650v. It was a nice chip. Topped out around 5300mhz on DICE.

I miss unlocking chips.

I certainly miss the notion; I was pretty disappointed when I found out FX chips could not be unlocked as well. Cutting the unused cores off I think? I don't know, something like that.

I've spent the last few days messing with this thing every moment I could. Loaded default values and popped my voltage to 1.4875V. Managed to squeeze a solid 3.4GHz out of the chip without any issues. The fourth core seems to really like negative ACC values for some reason; once I tried that again the BSODs went away. eh-smiley.gif

I basically got an X4 965 for like, $30, no complaints there. Thanks for the response, everything got worked out.

Quote:
Originally Posted by 1216 View Post

You mentioned everything appeared fine after removing RAM, have you tried raising CPU-NB voltage?

Yes. I don't remember what I raised it to (somewhere around 1.3V I believe......this board was NOT meant for overclocking so I'm trying not to get too carried away). I upped the HT link speed and the NB speed as well. With that and 1.55V I was able to hit 3.6GHz stable, but I felt like I was coming up on a heat wall because that chip runs WAY hotter than my X6 did on the same board. Thanks for the response, everything got worked out.
post #5 of 5
That ACC function was actually implemented with Phenom I Agena Based cpus as a cure for the TLB issues they had. This feature was carried on to Phenom II as some boards where compatible with both Phenom Core types.

It just so happens TLB is in all processors and is generally cured before release. AMD just shot for the "true quad core" feature at the time with Agena cores as a selling point. The lack of overclocking kind of made them look bad, then Phenom II came along pretty much the same cpu but with much higher clock capabilities.

A Phenom II 965BE for 30$ is a good deal. It's at least worth 10$ per core IMO. Nice find.
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