Does zip work on a 32-bit RISC OS ?

Alex Waugh alex at
Sat Oct 15 06:44:29 PDT 2005

In message <E1EPTQt-0007IT-8B at>
          Adrian Lees <adrian at> wrote:

> On Tue, 11 Oct 2005 you wrote:
> > I just see non 32-bit APCS code in GCCSDK zip (sendbits.s) file so this
> > probably means that the RISC OS zip binary doesn't work or work well on
> > a 32-bit RISC OS version (Iyonix, A9).  Can someone acknowledge this ?

I've been using zip on the Iyonix for a long time without problems.

> Whilst use of MOV/S/ pc,lr and LDMFD ...pc}/^/ are technically
> UNPREDICTABLE in User (and System) mode they are harmless on both
> the XScale and the ARM9, based on my experience and some quick
> tests. (In fact the first release of OpenVector and friends ran
> with many such instructions still in place due to an oversight on
> my part.)

The ARM968 will return the CPSR if you try and read the SPSR in user or
system modes, and thus a SPSR->CPSR copy effectively becomes a nop. I
expect the rest of the ARM9 family behaves similarly.


Alex Waugh                                           alex at

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