Complex sentence: It is difficult to determine exactly how Hercules emulation speeds correspond to real mainframe hardware partially due to the difficulty in comparing real mainframe hardware to other PCs and servers as well as the lack of a concrete performance measurement.
Split into simpler sentences: It is difficult to determine exactly how Hercules emulation speeds correspond to real mainframe hardware. This is partially due to the difficulty of comparing real mainframe hardware to other PCs and servers as well as the lack of a concrete performance measurement.