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Re: [MiNT] Scratch registers
On 12 Aug 2014 at 17:28, Miro Kropácek wrote:
> ggn wrote me: *My copy of ST Internals (circa 1988) states that for GEMDOS
> "In regard to all GEMDOS calls, it must be noted that registers D0 and A0
> are changed in all cases. If a value is returned, it is returned in D0, or
> D0 may contain an error number, and after the call A0 (usually) points to
> the stack address of the function number. Any parameters required in D0 or
> A0 must be placed there before GEMDOS is called."*
The very earliest official Atari GEMDOS documentation, dated 4 April 1986, says
(about the trap #1 call):
"Results are returned in D0. Registers D0-D2 and A0-A2 can be modified;
registers D3-D7 and A3-A7 will always be preserved."
That seems very clear to me.