simh simulation speed

From: Tom Jennings <>
Date: Mon Sep 27 17:00:08 2004

On Mon, 2004-09-27 at 14:27, John A. Dundas III wrote:

> However this does cause problems for some I/O devices. In some
> cases, extra code has gone into working through situations in which
> an OS makes implicit assumptions about how quickly an I/O operation
> will complete. Sometimes SIMH executes these too quickly and much
> fun ensues.

Good point!

The LGP-30 doesn't even have the hardware concept of "IO ready" for the
console flexowriter, relying entirely on drum software-delay routines to
avoid overrunning it, so I'll have to go look at how simh handles that.

I too quickly stated (duh) that I'll go add the sleep code to simh for
the LGP machines; it's not that simple. Drum machines have a
memory-search characteristic exactly analogous to a floppy sector skew
factor search; actual time to execute depends on the most-recent sector
(word) and the current instruction. It's not trivial, like it might be
with a core/semi machine.

SO I'll make my crappy sim into an LGP-xx simulator still.
Received on Mon Sep 27 2004 - 17:00:08 BST

This archive was generated by hypermail 2.3.0 : Fri Oct 10 2014 - 23:37:32 BST