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The only CPU families with HyperThreading are:
Pentium4
Atom
Core i3, i5 and i7
plus the xeon (server) versions of the above. Not all of the CPUs from any of these families have it enabled though.

Your Atom CPU can enable HT (if it isn't already - see how many cores show up in Task Manager), but as that CPU only has 512kB L2 cache, running 2 instances of Rosetta would almost certainly reduce throughput. I'd probably enable HT in the BIOS but set Rosetta to only use 1 core so other threads can run on the HT 'core' which should make it slightly more responsive than with HT off.

Your Mac won't have HT as it will almost certainly be Core2 based.

HTH
Danny

In the BIOS you can define whether you wish to enable hyperthreading, on some CPUs anyway. If it is enabled then it runs as though twice as many cores are available, and there is some extensions in the CPU that help it do so more efficiently then a CPU that is not hyperthread enabled.

Since most Rosetta calculations involve floating point arithmetic, one actual bottleneck becomes a shared resource that does the math rather then the CPUs. So some workloads run significantly better under hyperthreading, others, such as Rosetta that are so specific to arithmetic, don't get as much of a boost. In essence you still only have so many clock ticks (GHz) to spread around.