Hercules vs Sim390 - a comparison
Michael Short was so kind to run a
version ported to
emulator based system.
The different OS should have no sizable impact on the measured instruction
SVC and privileged instructions, which depend on
system response times, aren't covered.
A reference run with Hercules 4.0 on the same host CPU is available too.
The data and full analysis is under
The key findings are
- Sim390 is, on identical Host hardware, a factor is a factor 6.5 slower than Hercules 4.0, based on the lmark MIPS ratio of 6.39 to 41.54.
- simple instructions, like LR R,R, are about a factor 9 slower, see section LR timing.
- branch timing does not depend on same/different page, see section branch timing.
TRTare much faster on Sim390, see section CLCL+TRT performance.
The overall summary is that Hercules has a much more efficient handling of instruction fetch and decoding and virtual to real address mapping.
Any remarks and comments are very welcome.