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Journeyman III
Journeyman III

Dual 7702 CPUs perform worse than single!

Hello everyone. I purchased a supermicro dual mobo with two 7702's. The problem I'm having is that a single CPU installed is significantly outperforming the two when installed together. I've tested this with multi-threading applications like Maya, in which I both rendered and did fluid simulations. The RAM shows up in Windows 10 (512Gb), as well as the 256 threads, when both CPUs are installed. When running multi-threaded tasks the task manager shows all 256 threads active. So on the surface, everything looks like it's working, but the simulation/render times are at least 1/3rd less when just a single CPU is installed.

Any ideas what could be causing this?

*Note, I did have to fix the mobo's pins on socket 2. It arrived with a couple of pins out of place, but the machine wouldn't boot if the pins weren't aligned, so I can't see how this is a factor?

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Re: Dual 7702 CPUs perform worse than single!

Hello ralph7d7‌,

This probably boils down to the application specifically.  It may not be NUMA aware, therefore cannot handle the number of NUMA nodes being created by the BIOS and OS.  Windows will create multiple processor groups, each one with a maximum of 64 CPU threads.  So with a pair of 7702's you have 256 threads, or 4 processor groups.  Each processor group will result in a unique NUMA node.The application may being having an issue with 4 NUMA nodes.  Please read our Windows Tuning guide here:  https://docs.microsoft.com/en-us/windows/win32/procthread/numa-support

In case it's not something to do with the number of NUMA nodes, try adjusting the NPS setting in BIOS to NPS2 or 4, and see if this has any positive or negative impact.

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