I downloaded Cfish 9 from here: https://github.com/syzygy1/Cfish/releases
and I was able to install both of these engines:

cfish_9_haswell_bmi2_windows.exe
cfish_9_x64_bmi2_windows.exe

They both run on my computer but I am not sure which one should I use. Which one should I use if I want to use the stronger of the two?

Any help is greatly appreciated.

@roland23 wrote:I downloaded Cfish 9 from here: https://github.com/syzygy1/Cfish/releases
and I was able to install both of these engines:

cfish_9_haswell_bmi2_windows.exe
cfish_9_x64_bmi2_windows.exe

They both run on my computer but I am not sure which one should I use.  Which one should I use if I want to use the stronger of the two?

Any help is greatly appreciated.

Nothing changes, they are both for the same set of PEXT instructions (BMI2)

Thanks.