[HECnet] AXP Emulation

[Paul_Koning at Dell.com]

On Aug 9, 2012, at 6:10 PM, Dave McGuire wrote:

On 08/09/2012 04:07 PM, Sampsa Laine 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.

As far as I can understand, one MIPS is roughly one VUPS, correct?

More or less...depends on who you ask.

So how come I get 14 VUPS on the same host running SIMH whilst my Hercules install peaks at 180?

Ummm...because one is an IBM mainframe architecture and the other is a
VAX?   MIPS is a very, very different thing between different architectures.

True, but a 360 is also a CISC machine, somewhat simpler than VAX but not massively so.

On Aug 9, 2012, at 6:12 PM, Dave McGuire wrote:

On 08/09/2012 05:21 PM, Paul_Koning at Dell.com wrote:
...
I did notice that SIMH vax seems surprisingly slow, at least when running NetBSD.

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.

	paul