How to Test One Core at a Time

[Zathri]

I am interested in testing the CPU performance utilizing one core of a multi processor and core computer. The reason is because I have an old VB6 application that does not support mult-threading and will only utilize one core at a time. How can I set the software to do this? I did not see an option.

Thanks.

[David (PassMark)]

There is an option in the Edit / preferences window.
Set processes to 1.

[Zathri]

I was wondering if that setting was for # of cores or if it was number of processes at a time like in an IO test.

I set that to 1 and the computer still utilized both cores according to the CPU Usage History graph. I don't think the setting worked unless I have to run as an administrator or something.

[David (PassMark)]

The operating system might still distribute the load among available CPUs even with 1 process. This would also happen in your old VB6 application, you would see it moving between the available cores over time.

This is a normal part of CPU scheduling.
http://en.wikipedia.org/wiki/Scheduling_%28computing%29

2 processes with 2 cores would result in 100% CPU usage on both cores.
1 process with 2 cores would result in about 50% CPU usage on both cores.
1 process with 4 cores would result in about 25% CPU usage on all cores.

[Zathri]

Yeah, we would hope that the Windows Server 2008 OS would distribute the load, but in a process that takes hours only utilizes 1/8 cores at ~80% utilization. Although I'm not sure how the OS is viewing the process from the application, each step might be a different process. So it might not get a chance to balance across the cores?

[David (PassMark)]

CPU task scheduling is done around every 30 milliseconds in Windows. Unless special steps are taken to set CPU affinity, any single task tends to get rapidly (from a human point of view) shared around among available CPUs and cores.