How do I use Prime95 w/ my Q660?

Try Orthos, then you don't have to dick around with 4 instances of prime. Orthos will stress all simultaneously without you changing any settings. It will also stress your memory if u use the blend CPU and memory" test.

Do you have the latest version of Prime95? When I run it, it automatically runs 4 for me.

Evilonigiri is right. I have the latest version of prime95 too...and it stresses all cores automatically for me too. I didn't change anything...just intall and ran it.

My version of Prime95 uses all 4 cores, but not simultaneously. It goes from core to core eatch at 100% at a time; thus, the CPU load total never reaches 100%. I geuss I'll try Orthos, but is the memory test as good as Memtest86+?

You mean the blend test for the memory? It's to check that your ram is stable, while the memtest86 checks if your ram is good.

If your memory passes the blend test I would say that it doesn't have any issues, otherwise you should try memtest to make sure there are no serious problems. I always ran the CPU test first to rule that out as the reason for failing the blend test.

What version of Orthos are you using? I have a version from 2004 that uses two cores, but I still can't get it to work with cores 2 and 3, and two instences just use cores 0 and 1 together and completely leave cores 2 and 3 alone. If I could just be able to run more than one instence of Prime95, I would be in good shape too.

Let's see...run Orthos, hit Ctrl - Alt - Delete, click on the process tab, find Orthos, right click and hit set Affinity, de-select core0 and core1 and select core2 and core3. Then open up another Orthos and run them both.

Thank you guys so much for helping me out!   Thanks!

If you have a multi-CPU machine then you should run one instance of Prime95 for each CPU. If the cores share one memory controller then you'll probably get maximum stress by running the blend test on one CPU and running a small FFTs test on each of the other cores.
If you run Prime95 and then try to start another copy of Prime95, you only end up with one instance of the program running. In order to run two Prime95 tests at the same time, you need to invoke the program using the "A" command line switch. Make a shortcut to Prime95 and put it on your desktop. Then right-click drag and drop it onto the desktop and select "Create Shortcut Here" to create a copy of the original shortcut. Right-click the copy of the shortcut, select "Properties", and then select the "Shortcut" tab. Then go to the "Target:" field and add "-A1" to the end. If you want to be able to run more instances then create another shortcut copy with "-A2" and so on. Each shortcut will open up a separate instance of Prime95 so you can run more than one test at a time.



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I did as you suggest and got 4 core running. However, one core show this warning.
WARNING: Affinity Mask: Process: 0xC Sys: 0xF

What does it mean. thanks

Don't worry about it. It means some cores were disabled or such.

There's no need to run multiple instances of Prime95 anymore, nor is there any reason to switch from Prime95 to Orthos if you run multiple cores.

The newest version -Prime95 25.5- now supports multiple cores and 32- or 64-bit.

That's true, but I'm finding myself preferring Orthos to Prime95. Partly because Prime95 would crash whereas Orthos would actually report the error. And yes, I did enable round error checking.