Is it necessary to run two instances of Prime95 at the same time to stress test an Athlon 64 X2 system?

[Link19]

Is it necessary to do that and have one run on each separate CPU? Why does it only use 50% of your CPU when you run only one instance of Prime95? But with only a single processor, any games or Prime95 use 100% of your CPU cycles? I mean if the Affinity is set for all processes to use both CPUs by default, then why don't games and Prime95 use 100% of both CPUs by default on multi processor systems? They only use 50% of each? Why is that?

Does it have anything to do with whether the application you are running is designed to be SMP aware and benifit significantly from it?

 

[drwngflies]

If you're stessing to read correct MAX Temps, then, YES, You need two instances to heat up the core to max.
If you're only looking at whether or not an OC will produce errors, you could set affinity to a core then run P95, then set affinity to second core then re-run. But it's so much easier, since you have the ability to utilize both, why not use it?
The percentage of use, is of the total, so if one core is at 100% it will show only 50% used.
The affinity is to either utilize one core, or switch from one core to another, as needed.
So, if both were selected as usable, then it will decide which core has less load on it, then set the non-specific appl to use the less loaded core available.
Maybe I answered your questions, if not, post again, and I'll try again.

 

[Link19]

The other question I needed to ask was, why doesn't a game or application designed to use 100% of your CPU use 100% of both CPUs in a multi processor system? Is that because only applications that are multi threaded aware can utilize both cores at once where as single threaded applications can only take advantage of one CPU, so the OS just assigns it to use the CPU that is most available?

Also, if one instance of Prime95 fails, but the other keeps on going, does that mean I have a hardware problem and my system won't be rock solid and stable when running resource intensive tasks? or is it common for one instance of Prime95 to fail when running two as it it may not be designed for that purpose? Is Prime95 an SMP aware application?

 

[Gatt]

Originally posted by: Link19
The other question I needed to ask was, why doesn't a game or application designed to use 100% of your CPU use 100% of both CPUs in a multi processor system? Is that because only applications that are multi threaded aware can utilize both cores at once where as single threaded applications can only take advantage of one CPU, so the OS just assigns it to use the CPU that is most available?

Also, if one instance of Prime95 fails, but the other keeps on going, does that mean I have a hardware problem and my system won't be rock solid and stable when running resource intensive tasks? or is it common for one instance of Prime95 to fail when running two as it it may not be designed for that purpose? Is Prime95 an SMP aware application?

Well, in short, a game or app designed to use 100% of a single core isn't designed with Dual Cores in mind. Often Processor power is budgeted out carefully, such as in Doom 3's engine or Half Life 2's, and it's budgeted out with a single core processor in mind. Since a Dual Core has (Theoretically) twice the processing power, the budget only consumes half of the processors time when "spread" across two cores. Especially since those games/apps aren't multithreaded.

If one instance of prime fails, and the other continues, then one core is at/beyond it's limits. If you keep it OC'd at that level, one core may not be stable and cause problems.

It's also possible that the problem is the memory, I'd retest to rule out some random memory fault, and mess with timings/multipliers to try a lower memory speed with the same processor speed.

Case in point, my system craps out early right now. I'm using 2x 1gig 2-3-2-5 OCZ memory and a 4200+. The memory tops out around 210mhz with the processor around 2300mhz. The processors can handle more. So when I get around to it, I'll cut the timings and the multiplier and push the processor higher.

Prime isn't SMP aware. You need to run two instances at the same time to work both cores. One instance isn't sufficient.

 

[AkumaX]

Did we ever answer the question of what Torture Test to run in prime?

 

[Xenofin]

Originally posted by: AkumaX
Did we ever answer the question of what Torture Test to run in prime?

Hmmm.... It depends what you would like to stress during testing. If it is your CPU, use SmallFFTs, if it is your CPU&memory use large FFTs. Testing only with one core does not stress the system to the limit.

I have an experience with my system (X2 3800+ Manchester, OC@2450MHz, Vcore=1.475V), 4x512GB PC3200 Twinmos SpeedPro(?) 2.5-3-3-8, RAMdiv 333MHz, HTT=4, Multi=10) that I could run my CPU @2.5 GHz hours with Prime/SmallFFTs, but as soon as I used LargeFFts my CPU's core0 crashed after few minutes, mostly between 5-10 minutes in testing. I backed to 2.45GHz and CPU's both cores run now at least 3 hours stable with LargeFFts with CPUtemp 57-58C max. If CPUtemp goes over 60C -> core0 crashes (measured with ASUSProbe).

 

[Skott]

Whats the minimum/maximum time one should run Prime95? Seems most posts I have read around the net they havent bothered to subject their systems to more than 12 hours of Prime95. Wouldnt it be better to go at least 24 hours?

 

[imported_michaelpatrick33]

I get much higher temps when running S&M over Prime95 with my X2 system. I get around 47C at 2730 for my X2 4400+ on dual Prime95 but get around 55C at 2730 with S&M. You can also watch to see if you are throttling with S&M and you only need to run one instance for it will fully tap both cores.

 

[Diogenes2]

Originally posted by: Skott
Whats the minimum/maximum time one should run Prime95? Seems most posts I have read around the net they havent bothered to subject their systems to more than 12 hours of Prime95. Wouldnt it be better to go at least 24 hours?

Whatever satisfies you..


12 Hours, should be plenty.. I've had Prime fail after five hours, but then run longer on a subsequent test...

I try to go ahead and use the computer as I normally would while Prime is running.. Things might be a little choppy, but if everthing keeps working, it's a pretty good indication of a stable overclock..

You have to resist the urge to sqeeze every last mhz out of your OC.. The difference between 2.5 and 2.7 is less than 7%, while going from 2.0 to 2.5 is 20%.. You will find that application performance will follow that pretty closely.. Gaming will usually be less, since newer games are more GPU dependent.

How much time, where you are not getting anything else done, is it worth to boost performance by 7% or less?

Just something to keep in mind while you try to get your max OC..

 

[lopri]

If your computing pattern is light, I wouldn't say you should be Prime95 stable for longer than 30 mins. (That's what I use for initial test when I set a new clock) Problem/crash can happen with software also, not just with hardware. But if you use your system heavily, (gaming for hours) you'll definitely want to have your system stable for at least 6 hours, preferably 12 hours. More than anything, you get the peace of mind.

lop

 

[squigly]

I couldn't seem to find this answer by searching so, how do you get tow instances of prime to run at the same time?

Thanks

 

[Diogenes2]

Originally posted by: squigly
I couldn't seem to find this answer by searching so, how do you get tow instances of prime to run at the same time?

Thanks

You have to put 2 copies of P95 in seperate folders. Start both programs, pause execution then use the ' advanced ' tab to set the affinity for each CPU.

 

[squigly]

Thanks, I'll give that a try when I get home.

 

[Link19]

When I run two instances of Prime95 with In-Place Large FFTs (one for each core), one of the cores fails while the other keeps running perfectly. Does that mean I have a hardware problem for sure? Or is it normal for it to fail with two instances of In-Place Large FFTs?

 

[aka1nas]

Is this overclocked or at stock? If Oced, then perhaps one core is not as good of an OCer as the other.

 

[evilharp]

Originally posted by: Link19
When I run two instances of Prime95 with In-Place Large FFTs (one for each core), one of the cores fails while the other keeps running perfectly. Does that mean I have a hardware problem for sure? Or is it normal for it to fail with two instances of In-Place Large FFTs?

Large FFT failure can mean Core or Component or Ram failure.

Run 2 Small FFTs, if they pass the core is good (if you are OCing, and the cores fail, you aren't 100% stable, reduce speed). Then test the ram using S&M or memtest (use the new version). If the ram passes, it is something else (mobo/PSU/etc...)

Make sure that:
1) the affinity is set for each instance of Prime95 (S&M automatically attacks both cores)
2) you are using the correct X2 driver
3) you have the hotfix installed (with the Registry key set to 1)

 

[Link19]

When running two small FFTs, one of them fails eventually too even running at stock speed. In fact, I haven't even tried overclocking anything yet. I have a good PSU which is a SeaSonic S12 600WATT.

 

[Link19]

BUMP

 

[Link19]

MemTest 1.65 (the latest version) has so far been running for 8 hours and has passed 8 times without any errors.

 

[evilharp]

Hey Link19,

Ok, so the ram seems to be good. And, as you indicated, you should have a good PSU.

Now for some questions:

1) What motherboard are you using?
2) When you assembled your system, did you connect all of the power connectors (ATX main + 12v (4-Pin Square connector) + SLI connector (if applicable))
3) What are your temps (idle/load/ambient)?
4) What CPU are you using? What cooling solution are you using with it (stock cooler or aftermarket)?
5) What bios version are you running for your board (newest/beta/tweaked special)?
6) Are you using the X2 driver?
7) Did you get the dual-core hotfix, and set the registry key?

Let us know, and maybe someone can give you a specific answer.

 

[Link19]

Originally posted by: evilharp
Hey Link19,

Ok, so the ram seems to be good. And, as you indicated, you should have a good PSU.

Now for some questions:

1) What motherboard are you using?
2) When you assembled your system, did you connect all of the power connectors (ATX main + 12v (4-Pin Square connector) + SLI connector (if applicable))
3) What are your temps (idle/load/ambient)?
4) What CPU are you using? What cooling solution are you using with it (stock cooler or aftermarket)?
5) What bios version are you running for your board (newest/beta/tweaked special)?
6) Are you using the X2 driver?
7) Did you get the dual-core hotfix, and set the registry key?

Let us know, and maybe someone can give you a specific answer.

1. The motherboard I am using is a DFI NF4-DAGF.

2. Yes, all power connectors are plugged in.

3. Well, my CPU temperature is around 25C when at idle and around 36C when running Prime95 with one instance for each core. I don't know if the 25C seems right, but that is what it tells me in the BIOS and wth NV Monitor when not under load. CPU is running at stock speed.

4. The CPU I am using is an Athlon 64 X2 3800. The cooling solution I am using is a Thermalright XP-120 heatsink with a 56CFM airflow 120mm fan running full speed all the time. The thermal paste I have applied is Arctic Silver 5.

5. The BIOS version I am using is the latest which is dated 8/11/2005. See it here: http://us.dfi.com.tw/Support/Download/b...CATEGORY_TYPE=LP&STATUS_FLAG=A&SITE=NA

CPU and RAM is all running at stock speed. I have disabled Cool and Quiet, CPU Spread Spectrum, and all BIOS caching and shadowing options.

6. No, I am not using the X2 driver. You are not supposed to use the X2 driver unless you have Cool and Quiet enabled right?

7. Yes, I have the dual core hotfix installed because I slipstreamed a post Windows XP SP2 update pack (http://ryanvm.msfn.org/updatepack.html) into my XP SP2 installation source and that update pack contains the dual core hotfix. No, I haven't applied any registry key regarding this. However, isn't the dual core hotfix only necessary to apply if you have Cool and Quiet enabled? I don't have Cool and Quiet enabled, so does that hotfix and the registry key really even matter? Is it possible that having that hotfix applied could cause problems like this if it is not needed?


Now, just to give everyone a heads up on what actually happens. When running two instances of Prime95 with one instance for each core, only one instance fails. The other keeps on going perfectly forever. I have tried running only one instance for each core spearately, and they both run perfectly for a while without any errors. So, one specific core doesn't appear to be the culprit. Something just doesn't appear to be right only when both cores are being stressed to their maximum? Either that, or Prime95 has a problem running tow instances on some systems. What I do know is that I have tried running two instances of Prime95 for a Pentium 4 hyperthreading CPU with one instance for each logical CPU. And one instance would always automatically just shut down when I tried this on a HT P4 system. I am not sure if that has any relevance to a dual core CPU system? The version of Prime95 I am using is the latest version and also was for the P4 system I tried two instances on.

 

[evilharp]

Hey Link,

With a DFI board, you should hit up the DFI-Street forums. That is an awesome resource for DFI users. The boards are awesome, but they can be a PITA to set up (voltages/etc...)

Your temps look ok (nice and low!), but I've never seen a loaded X2 run in the 30's when loaded. Could be a sensor calibration issue...

With the bios, did you specify a CPU voltage or leave on auto?

The X2 driver does enable Cool and Quiet (CnQ), but it may do more. Most X2 users have installed it. You may want to try it (just set your Power Scheme to "Home/Office Desk" to disable CnQ in windows). For some users (me included) the X2 driver forced XP to recognize my CPU correctly.

If you have the hotfix installed, try setting up the registry key (1 to enable hotfix, 0 to disable). I found that it cleared up problems I had with my X2 even when I had CnQ disabled. XP wasn't built for dual-core, and though the NT kernel is compatible with dual-cpu systems it has issues with dual-core systems. The hotfix addresses these problems. With the hotfix I haven't had to mess with affinity or CnQ to get applications to work flawlessly.

Good luck.

 

[evilharp]

Originally posted by: Link19

Either that, or Prime95 has a problem running tow instances on some systems. What I do know is that I have tried running two instances of Prime95 for a Pentium 4 hyperthreading CPU with one instance for each logical CPU. And one instance would always automatically just shut down when I tried this on a HT P4 system. I am not sure if that has any relevance to a dual core CPU system? The version of Prime95 I am using is the latest version and also was for the P4 system I tried two instances on.

Prime95 will only run on a true core. Hyperthreading is not really dual-core, so I am not surprised that dual instances failed on the P4.

I've run 2 instances on my X2 for 12hours+ without failures, and I have seen 8 sessions run on an old Compaq 8-way Xeon server. Prime95 shouldn't be the problem here.

 

[rise]

Originally posted by: Link19
6. No, I am not using the X2 driver. You are not supposed to use the X2 driver unless you have Cool and Quiet enabled right?

no, install the x2 drivers.

7. Yes, I have the dual core hotfix installed because I slipstreamed a post Windows XP SP2 update pack (http://ryanvm.msfn.org/updatepack.html) into my XP SP2 installation source and that update pack contains the dual core hotfix. No, I haven't applied any registry key regarding this. However, isn't the dual core hotfix only necessary to apply if you have Cool and Quiet enabled? I don't have Cool and Quiet enabled, so does that hotfix and the registry key really even matter? Is it possible that having that hotfix applied could cause problems like this if it is not needed?

again, no. as harp said you may not need it. i didn't need it to run 2x primes but if you have problems with oother apps you may want to enable it. but it really doesn't matter if you're using cool n quiet or not as far as i can tell.

alot of peoople, like me, have CnQ bios disabled and the fix helped some game issues.

Now, just to give everyone a heads up on what actually happens. When running two instances of Prime95 with one instance for each core, only one instance fails. The other keeps on going perfectly forever. I have tried running only one instance for each core spearately, and they both run perfectly for a while without any errors. So, one specific core doesn't appear to be the culprit. Something just doesn't appear to be right only when both cores are being stressed to their maximum? Either that, or Prime95 has a problem running tow instances on some systems. What I do know is that I have tried running two instances of Prime95 for a Pentium 4 hyperthreading CPU with one instance for each logical CPU. And one instance would always automatically just shut down when I tried this on a HT P4 system. I am not sure if that has any relevance to a dual core CPU system? The version of Prime95 I am using is the latest version and also was for the P4 system I tried two instances on.

i know my ultra-d and sli-dr all undervolt the vcore abit. i didn't keep my infinity long enough to remember if it did the same but maybe kick your vcore up a notch just to see.

 

[Link19]

Originally posted by: evilharp
Hey Link,

With a DFI board, you should hit up the DFI-Street forums. That is an awesome resource for DFI users. The boards are awesome, but they can be a PITA to set up (voltages/etc...)

Your temps look ok (nice and low!), but I've never seen a loaded X2 run in the 30's when loaded. Could be a sensor calibration issue...

With the bios, did you specify a CPU voltage or leave on auto?

The X2 driver does enable Cool and Quiet (CnQ), but it may do more. Most X2 users have installed it. You may want to try it (just set your Power Scheme to "Home/Office Desk" to disable CnQ in windows). For some users (me included) the X2 driver forced XP to recognize my CPU correctly.

If you have the hotfix installed, try setting up the registry key (1 to enable hotfix, 0 to disable). I found that it cleared up problems I had with my X2 even when I had CnQ disabled. XP wasn't built for dual-core, and though the NT kernel is compatible with dual-cpu systems it has issues with dual-core systems. The hotfix addresses these problems. With the hotfix I haven't had to mess with affinity or CnQ to get applications to work flawlessly.

Good luck.

Thanks for the suggestions.

Regarding the X2 driver, what made me worried about installing was what I saw on the DFI website page listing the drivers for my motherboard.

You can see it here: http://us.dfi.com.tw/Support/Download/d...&INDEX_TYPE=null&STATUS_FLAG=A&SITE=NA

It says in RED letters to not install it if you are overclocking. Now while I don't have my system overclocked, I do plan to eventually overclock it. I just want to make sure that my system is 100% rock solid stable at stock speeds first before I attempt any overclocking.

Is that AMD driver on the DFI website listing the drivers for my motherboard the same X2 driver you are talking about? If it is, why does it say it in red to NOT install it if you are going to overclock?