Re: [B2-devel] Patches for Real Addressing

[Christian B. <cb...@st...>]

Hi!

On Thu, Sep 21, 2000 at 12:07:40PM +0200, Gwenole Beauchesne wrote:
> I determined that the unfriendly code starts at ROMBase + 0xdb9c.

Some internal Memory Manager code...

> Bit 0 of the byte located at 0x1efc (what is it ?) is always tested.

This bit specifies whether the MM is in 32 or 24 bit mode.

> for some reason, at the end of the Speedometer Graphics test, the branch
> with the stripping by AND'ing with Lo3Bytes is taken!

Probably a Speedometer bug. It shouldn't be possible/necessary to switch
to 24 bit addressing under B2.

> 0x48e7, 0x1c20, // movem.l      d3-d5/a2,-(a7)
> 0x382e, 0x0008, // move.w       $0008(a6), d4
> 0x3a2e, 0x000a, // move.w       $000A(a6),d5
> 0x554f,         // subq         #$2,a7
> 0x3eb8, 0x028e, // move.w       ROM85,(a7)

Looks like it should be "move.w #ROM85,(a7)" here.

> 0x301f,         // move.w       (a7)+,d0
> 0x48c0,         // ext.l        d0
> 0x2440,         // movea.l      d0,a2
> 0x2040,         // movea.l      d0,a0
> 0x3010,         // move.w       (a0),d0
> 0x0c40, 0x3fff, // cmpi.w       #$3fff,d0
> 0x6316          // bls.s        #$00000016

Very ugly code, BTW. Seems that Apple didn't have the money for a decent
C compiler...

Bye,
Christian

-- 
  / Coding on PowerPC and proud of it
\/ http://www.uni-mainz.de/~bauec002/