does rosetta normally use the FPU? ALU? both? is using both at the same time possible without hyperthreading?

AFAIK, Rosetta is bound by FPU performance. As for using both, yes it is possible, as most modern CPUs are Superscalar. That means that it will try to use all of the execution units available (ALU, FPU, SIMD). However, programs don't always have a good mix of instructions that utilize all the units fully. That's where SMT (hyperthreading) steps in because there is a better chance of using all the resources when there are more instructions to pick from.

Since Rosetta contains mostly FPU instructions and is not highly bandwidth constrained, it does not benefit as much from SMT as would other applications.

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R@H clearly uses the floating point side of the CPU. It does not appear to take full advantage of SSE or other instruction sets.

The conventional wisdom is that R@H runs best with a large L2 cache. For this reason, most people disable HyperThreading. The idea is that two work units using the same cache will receive only 1/2 the cache resources.

I have 2 identical systems and planned to test 1 with HT and 1 without. To date, I have not done the test. I keep HT enabled thinking it will make sure no clock cycles are ever wasted on the CPU.

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Thx!

Paul

Paul, I might save you the time. I set one of my hosts to not do HT several months ago.

RAC 181 with no HT

RAC 257 with HT

So, you're thought seems to be right, HT assures less ticks slip away unused.

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Add this signature to your EMail:
Running Microsoft's "System Idle Process" will never help cure cancer, AIDS nor Alzheimer's. But running Rosetta@home just might!
https://boinc.bakerlab.org/rosetta/

I forgot, my HT machine also has Ralph running when work is available. So, it's RAC would be even higher if 100% on Rosetta.

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Add this signature to your EMail:
Running Microsoft's "System Idle Process" will never help cure cancer, AIDS nor Alzheimer's. But running Rosetta@home just might!
https://boinc.bakerlab.org/rosetta/