Re: SIMH CPU-idleing support

[David Brownlee <abs%netbsd.org@localhost>]

On 18 November 2010 07:18, Matthew Mondor <mm_lists%pulsar-zone.net@localhost> 
wrote:
> On Thu, 18 Nov 2010 07:52:15 +0100 (CET)
> Peter Svensson <petersv%psv.nu@localhost> wrote:
>
>> 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)).
>
> This is also the impression that I got reading the related SIMH code.
> Also, after Der Mouse's reply I decided to do some searches and it
> seems that in example code like the one at
> http://pupgg.princeton.edu/cdrom12/html/ssb71/4556/4556p002.htm it
> still indeed has to poll and wait regularily to simulate an "idle
> enough" loop, confirming that a "proper" wait-for-interrupt instruction
> is missing.
>
> If SIMH can be adjusted for NetBSD-5 that'd still be great though, it's
> worth looking into.
>

Would there be any sense in adjusting NetBSD's idle loop to play well
with SIMH and other emulators? Providing it doesn't impact performance
on real hardware :)