[hatari-devel] Perhaps this evocate something to you...

[Laurent Sallafranque]

A good candidate for testing 16Mhz vs 32 Mhz is Watership.

It loads quickly and bugs immediately at 16 Mhz (but runs at 32Mhz).

I've taken 2 CPU traces : one at 16 Mzh and one at 32 Mhz and I've made 
a diff of the 2 traces.

Here is the result :

The 2 programs are running the first 3196 instructions the same way.
Here are the latest instructions ran by both tests :

...
0002E226 4298                     CLR.L (A0)+
0002E228 51c9 fffc                DBF .W D1,#$fffc == $0002E226 (F)
0002E226 4298                     CLR.L (A0)+
0002E228 51c9 fffc                DBF .W D1,#$fffc == $0002E226 (F)
0002E226 4298                     CLR.L (A0)+
0002E228 51c9 fffc                DBF .W D1,#$fffc == $0002E226 (F)
0002E226 4298                     CLR.L (A0)+

At line 3197, the 32 Mhz test continues to run the same 2 instructions 
as above.

But the 16 Mhz test does :

00E03C50 52b9 0000 04ba           ADD.L #$00000001,$000004ba
00E03C56 e7f9 0000 11ba           ROLW.W $000011ba
00E03C5C 6a48                     BPL.B #$00000048 == $00E03CA6 (F)
00E03C5E 48e7 fffe                MOVEM.L D0-D7/A0-A6,-(A7)
00E03C62 614a                     BSR.B #$0000004a == $00E03CAE
00E03CAE 48e7 c080                MOVEM.L D0-D1/A0,-(A7)
00E03CB2 2038 11bc                MOVE.L $000011bc,D0
00E03CB6 677a                     BEQ.B #$0000007a == $00E03D32 (T)
00E03D32 4cdf 0103                MOVEM.L (A7)+,D0-D1/A0
00E03D36 4e75                     RTS.L
00E03C64 0838 0001 0484           BTST.B #$0001,$00000484
00E03C6A 672a                     BEQ.B #$0000002a == $00E03C96 (F)
00E03C6C 4a38 11b1                TST.B $000011b1
00E03C70 6724                     BEQ.B #$00000024 == $00E03C96 (T)
00E03C96 3f38 0442                MOVE.W $00000442,-(A7)
00E03C9A 2078 0400                MOVEA.L $00000400,A0
...


At line 4653, the 32 Mhz test does :

0002E228 51c9 fffc                DBF .W D1,#$fffc == $0002E226 (F)
00E03C50 52b9 0000 04ba           ADD.L #$00000001,$000004ba
00E03C56 e7f9 0000 11ba           ROLW.W $000011ba
00E03C5C 6a48                     BPL.B #$00000048 == $00E03CA6 (T)
00E03CA6 11fc 00df fa11           MOVE.B #$df,$fffffa11
00E03CAC 4e73                     RTE.L
0002E226 4298                     CLR.L (A0)+
0002E228 51c9 fffc                DBF .W D1,#$fffc == $0002E226 (F)
0002E226 4298                     CLR.L (A0)+
0002E228 51c9 fffc                DBF .W D1,#$fffc == $0002E226 (F)
0002E226 4298                     CLR.L (A0)+
0002E228 51c9 fffc                DBF .W D1,#$fffc == $0002E226 (F)


Both tests are jumping to address $E03C50, but not after the same amount 
of instructions.

The test after the first 3 instructions after the "interrupt" is TRUE 
for the 32 Mzh test, but is false for the 16 Mhz test.

The 32 Mhz test continues to CLR / DBF whereas the 16 Mhz test goes into 
completely different code.

Does this mean something to you ?

Regards

Laurent