Re: SIMH CPU-idleing support

[Peter Svensson <petersv%psv.nu@localhost>]

On Thu, 18 Nov 2010, Anders Magnusson wrote:

> AFAIK there are no way to wait on any VAXen, so the only way for an
> emulator to save cycles would be to detect the idle loop in some way.

SIMH detects the idle loop by detecting the number of cycles spent at a 
specified IPL. I think. It can be adjusted (the SET IDLE NETBSD sets the 
idle detector to wait for 1000 instructions at IPL 1 (ipl_mask=0x02)).

Which IPL is theNetBSD idle loop run at?

For idle handling to work you will probably need some patches from 
http://sourceforge.net/projects/simh/files/ (vax-idle at least).

Peter