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
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