[HECnet] AXP Emulation

[Dave McGuire]

On 08/09/2012 08:50 PM, Paul_Koning at Dell.com wrote:
Why is SIMH so slow though?

Because it's extremely portable with no architecture-specific 
assembler assists.   As I won't use anything that's NOT portable, I 
consider it to be screaming fast.

I don't know about Hercules, but dtcyber is all C code, and it seems
to be substantially faster than simh.

  ...and it also only emulates one architecture.   Simh has an underlying
emulation framework upon which emulations for many disparate
architectures can be constructed.   There is (as I'm sure you know)
always a cost to this sort of flexibility.

  At least that's my take on it.

VAX is a "big" architecture and instruction set to emulate.

That's true, but that doesn't mean any one instruction is hard to
emulate, it just means there's a lot of code.   Well, the packed
instructions, and edit, and stuff like that, sure, but when you're
running NetBSD makefiles and compiles you're basically in the world
of integer instructions, and those aren't particularly hard.

Maybe it's time to do some code analysis and profiling.

  I think that's a fine idea.

                      -Dave

-- 
Dave McGuire, AK4HZ
New Kensington, PA