I check this blog regularly. You never mention that speedstep works on SSE2, last post about SSE2 has
Also u can find sse3/sse2(unversal) kernel which should be able to sleep(even on sse2) if ur hardware sllows to sleep with osx. this kernel can’t make speedstep
I check 10.5 channel and there are kernels as follow
9.1.0 speedstep/intel/amd/sse3 kernel
9.0.0/speedstep sse3 kernel
sse2 10.5.1/10.5 kernel
9.1.0/9.0.0 sleep sse3/sse2 kernel
With one has speedstep. I am talking about SSE2 not SSE3 kernel