[Simh] SIMH and Compiler Profiling

[Paul Koning]

> On Dec 8, 2015, at 10:47 AM, Henry Bent <henry.r.bent at gmail.com> wrote:
> 
> Hi all,
> 
> ...
> Results, higher numbers are better:...
> As you can see, the performance improvements are fairly dramatic, with gcc improving an average of 66%.  Of course, one benchmark is not necessarily indicative of a real life workload; the most appropriate improvements would probably be made by profiling using whatever workload your system generally runs.  This was merely meant to illustrate what sort of gains are possible.

Interesting.  I would expect profiling to be most helpful for code that has some well defined hot spots, and computer emulators seem to be a good fit for that pattern.

> I find it fascinating that a Q9500 can be almost as fast, or faster, than a real NVAX workstation.  I imagine that the most modern Intel processor would probably be faster than any real VAX.

I'm amazed that a real VAX would be anywhere near as fast as a modern PC running the emulator.  Perhaps I'm mislead by PDP11 emulation, which has for ages now been vastly faster than the real machines.  (Ditto CDC 6000 series, for that matter.)

The other interesting thing is that GCC is better than ICC.  That's a bit surprising since ICC is totally focused on being a good Intel compiler, while GCC is a many-platforms portable compiler.  

	paul