Do rounding errors in Prime95 automatically = instability?

I have my XP 1800+ running at 1.8ghz (156fsb). Everything seems totally stable. I can run 30+ loops of SiSoft burn-in (runnning CPU Bench, Multimedia bench, and Memory Bench in a continuous loop). I have make numerous 3dmark2k1 runs -- all without a hitch, and can run Seti forever.

However, when I run Prime95 torture test I will get a rounding error between 10-30 minutes into the test. No crashes -- it just reports the error (hardware failure) and stops.

Is my system by definition unstable? It seems to rock stable -- and I have to say I am in love with having my rig at a nice round 1.8 ghz (actually 1794mhz -- but close enough).

I am running at 2.17 Vcore (2.10 under load). My 5v Rail never drops below 5.08. My temps as reported by MBM5 never get above 42c (water cooled).

The rest of my rig specs are here.

Thanks for the help.

Dont you hate that.
I have the opposite problem.
When I try my xp at 1725 prime 95 works fine but 3dmark 2000 always locks up my pc in a certain test.
I think prime 95 has more to do with memory stability than cpu so maybe tweaking the memory or giving it a voltage nudge might help.

well skrill I have the same prob...............I get rounding error all the time on torture test. I haven't had anything lock my system up, until the other day..........I was doing some massive photoshop editing and it locked........So I've come to the conclusion that its about 95% stable........no games or anything lock it up but photoshop..........anyway I would try as many things as u can think of just to be sure.........I thought mine was 100% stable too until the other day.....

The Prime 95 torture test is extremely demanding, and the smallest error will cause it to stop, you most likely will not encounter any huge stability problems unless it will only go for less than a minute. Most computers-- even at stock speeds can not even last 2 hours of prime 95. You may have a crash or lockup every few days, but no serious problems. My system can go for over 24 hours of prime 95 with no errors, however, and it has gone for over a week, under load, without as much as a reboot.

If you get round off errors it means that *something* isn't stable. I can usually determine what it is by running it while testing for my top overclock. I put the multiplier WAY below spec (3 or 4 if possible) and the bump the FSB up. When P95 fails, that's tops for the bus, so I knock that down to the last stable speed and the bump the multiplier up till that gets stuck. That way you know which is your problem. So maybe try lowering your mult by like 4 or so and seeing if you still have problems.

Well am not sure Prim95 will tell you for sure if you have a stable system I found I had to get vmem to 2.6 to get my system stable in a few games. Even thought I ran the Prime test to its end

Thelemac said:

If you get round off errors it means that *something* isn't stable. I can usually determine what it is by running it while testing for my top overclock. I put the multiplier WAY below spec (3 or 4 if possible) and the bump the FSB up. When P95 fails, that's tops for the bus, so I knock that down to the last stable speed and the bump the multiplier up till that gets stuck. That way you know which is your problem. So maybe try lowering your mult by like 4 or so and seeing if you still have problems.

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This is great advice! I think he needs to unlock it first but still a great thing to test before you get started! I was wondering what you vcore and temps are at 11.5x156.

Thanks for the advice guys.

Last night I tried running Toast (the CPU stability test/heater). It heated up my CPU to 46c (4c higher than any other bench) -- but my system never hung and never crashed. It was like a rock. Ran it for two hours at high priority -- even surfed the web while it was running.

Now, this weekend I am going to back her down to 154 fsb and try running Prime -- I am betting she will make throught the torture test just fine.

To answer your questions -- I am running at 2.15 Vcore, 2.8 Vdimm. My temps are 42c under load (Seti, Prime etc.) (only Toast heats it to 46c). My system temp is 28c and my ambient is 23c.

i think prime is much more sensitve to even the slightest cpu error becuase its made to do complex mathamatics

but i mean if it can run for 10-30 min with out haveing anysort of errors your system is like 99.9999 stable and if you can live with that then thats cool if not back it down a little.