[hatari-devel] small bug in emutos with cartridge

[Nicolas Pomarède <npomarede@xxxxxxxxxxxx>]

Hello

adding TT ram raises quite a lot of problems, because it implies to run 
the cpu with 32 bit addressing, while up to now Hatari was more likely 
to run in 24 bit mode.

In 24 bit mode, upper 8 bits are ignored, so if an address has "garbage" 
in the upper byte, it is masked anyway with something like 0x00ffffff.

So, while booting emutos 0.9.3 with my devel version in 32 bit mode,I 
notice I get a crash during the boot (it displays emutos' debugger 
screen  after a bus error).

The problem is when emutos tries to run our cartridge code located at 
$fa0000 that we use for HD emulation.

Emutos does :

$e0010e : 41f9 00fa 0000                       lea       $fa0000,a0
$e00114 : 0c98 abcd ef42                       cmpi.l    #$abcdef42,(a0)+
$e0011a : 6600 0020                            bne       $e0013c
$e0011e : 0128 0004                            btst      d0,4(a0)
$e00122 : 6700 0010                            beq       $e00134
$e00126 : 48e7 fffe                            movem.l   d0-d7/a0-a6,-(sp)
$e0012a : 2068 0004                            movea.l   4(a0),a0
$e0012e : 4e90                                 jsr       (a0)


But the TOS does :

$e00bbc : 41f9 00fa 0000                       lea       $fa0000,a0
$e00bc2 : 0c98 abcd ef42                       cmpi.l    #$abcdef42,(a0)+
$e00bc8 : 6622                                 bne.s     $e00bec
$e00bca : 0128 0004                            btst      d0,4(a0)
$e00bce : 6716                                 beq.s     $e00be6
$e00bd0 : 48e7 fffe                            movem.l   d0-d7/a0-a6,-(sp)
$e00bd4 : 2028 0004                            move.l    4(a0),d0
$e00bd8 : c0bc 00ff ffff                       and.l     #$ffffff,d0
$e00bde : 2040                                 movea.l   d0,a0
$e00be0 : 4e90                                 jsr       (a0)


See the difference ? Address is masked with $ffffff before doing the 
jsr. In Emutos, the jsr is made directly without masking, but as the 
value at $fa0008 is 08FA023E ... bang! bus error in 32 bit mode :(
(upper byte at $fa0008 is used to choose the boot order, so it's not 0)

So, emutos can't run for now in TT mode with the 68030 in 32 bit mode 
and HD emulation (using fake cartridge at $fa0000) at the same time 
under Hatari.

A new 0.9.4 version will be needed soon :)


Nicolas