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Prime 95 small FFT fail and memtest fail... CPU or RAM problem?

Last response: in Overclocking
May 11, 2010 10:07:15 PM

So I have a super old pentium 4 system that I'm trying to overclock 4% (as high as it will let me) from 3.4 to 3.53, and the FSB from 200 to 208. The system becomes completely unstable afterwards.

So I ran a small FFT P95 test (the one that fits on the L2 cache on the CPU), and that failed a few minutes in, and I ran test 7 on memtest, which failed instantly. Test 5 on memtest, which is the test that's good at seeing if you're getting enough dimm voltage, actually completed a few rounds before it failed.

So... based on these results, it seems to me that my CPU isn't getting enough voltage, as test 5 would probably fail just as fast as test 7 if my memory wasn't getting enough voltage. In other words, the memtest errors are from the CPU. But on the other hand, even the small FFT test on P95 still uses a tiny bit of memory, so I could be wrong. My temps are no higher than they are when I'm not "overclocking".

What do you guys think?
a b à CPUs
May 12, 2010 3:29:17 AM

Have you tried running p95 and memtest at stock settings? Your system might be unstable already in its stock state, maybe bad psu, bad ram contacts, etc.
May 12, 2010 9:40:29 AM

My system is rock solid at stock speeds. I can run prime 95 and memtest all day.
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May 12, 2010 11:19:31 AM

I have a shutdown problem too!
a c 100 K Overclocking
a b à CPUs
May 12, 2010 5:46:20 PM

It's memory. You should reduce the memory multiplier since increasing the FSB will also increase memory speed. With the memory underclocked, get the CPU stable, then go back to figuring out the memory. Generally tho, if you increase the latencies it also might work. For instance, my RAM is rated at 1600mhz, 8-8-8-24, but I have it up at 1750 9-9-7-24 (althout that 7 doesn't seem to help with the latency in Everest benchmark). If you don't want to increase the latency and keep a higher speed, then it's just not enough voltage. The point of Memtest is to not test the CPU so it's pretty much gotta be a memory issue. Although, I'm not entirely sure which memtest you're using, I use MemTest86+ and as far as I know there's no selection of which test to run - regardless, you probably should just let it run all tests.
May 13, 2010 12:07:22 AM

Thanks Wolfram23. I changed the timings, now everything's working fine under a 4% bus increase.

I can't change the multiplier or anything like that, my motherboard is a simple intel model (D875pbz) that only has the 4% overclock feature to test for stability.

So, to get back to my original timings, I think I'll do another vdimm volt mod (no voltage tuning in BIOS). I already had to do that to increase my board by .05 volts to accomodate my RAM at factory timings. Another .05 or so should allow it to handle the 208 FSB as well.
a c 100 K Overclocking
a b à CPUs
May 13, 2010 5:10:39 AM

Glad I could help :)