Diff between 11/20 and 11/45?

Dave Horsfall dave at fgh.geac.com.au
Wed Sep 8 11:15:48 AEST 1999

On Mon, 6 Sep 1999, Carl Lowenstein wrote:

> The first genuine user-mode difference that I remember coming across was
> an incompatibility in the result of
> 	MOV SP, -(SP)

Anything involving the same register as src and dst in this way was,
err, different...

And I have an annotation that the JSR does not behave as documented.
Unlike page 91, the sequence is not (tmp) <- (dst) / v(SP) <- reg /
reg <- PC / PC <- (tmp).  The first ISP code is not present i.e. the
SP is decremented first, not saved, and the last is PC <- (dst).

> It isn't really clear to me why one would want to use this particular
> instruction, however it turned out to hang both BASIC and FOCAL at the
> time.  A zero-length patch wasn't too hard to figure out.

Some sort of frame pointer linking, on an architecture that didn't
have separate frame pointers (like the Vax)?

Dave Horsfall VK2KFU  dave at geac.com.au  Ph: +61 2 9978-7493 Fx: +61 2 9978-7422
Geac Computers P/L (FGH Division) 2/57 Christie St, St Leonards 2065, Australia

Received: (from major at localhost)
	by minnie.cs.adfa.edu.au (8.9.3/8.9.3) id LAA03594
	for pups-liszt; Wed, 8 Sep 1999 11:05:14 +1000 (EST)

More information about the TUHS mailing list