Have you tried writing the ROM with the routine I give in a separate FlashROM or SRAM cartidge and insert it in a slot other than carnivore2 to see if it works that way, and eventually reverse the cartridges?
I've played around a bit with gdx's code and a few tools and came to the conclusion that this method indeed works, but it also disables Nextor. The firmware checks for the presence of C9 at the hook and copies its call there in case of a match. If we remove C9, then the firmware won't start, but at the same time Nextor will not find C9 and will pass control to the hook, assuming that something else needs to start. And the control is not passed back to Nextor after that "something" exits. As a result, we will have only Basic and no working drive(s).
The simpliest way out is to prevent Nextor from passing control in case C9 is not found. Simple patch - only 2 places to hack. But I want to have a more elegant solution than the bloody hack. A separate ROM starts too soon to overwrite the firmware's hook and too late, when Nextor has already exited.
I may have misdirected the hook or else it's the Carnivore2 who doesn't take this possibility into account. Could I try the ROM you created on OpenMSX to try to see what is causing the problem?
DOS2/Nextor checks H.STKE in H.RUNC handler.
When H.STKE is hooked,
and if USRTAB == FCERR, then it run in DOS1 mode,
or if USRTAB != FCERR, then it run in DISK-BASIC2/Nextor-BASIC mode.
H.RUNC is called after all slot initialization, before H.STKE by BIOS.
H.STKE is needed to set before build-in firmware initialization.
H.STKE is needed to clear before H.RUNC handler of DOS2/Nextor.
There is SKIPFIRM.ROM for bybassing firemware.
SKIPFIRM.ROM is needed to insert on slot after Nextor slot, before firmware slot.
For carnivore2 with default configration,
SKIPFIRM.ROM should be mapped to mapper slot X-2 or FMPAC slot X-3 or later another slot.
;sjasmplus
output "SKIPFIRM.ROM"
Z80_OPCODE_RET equ 0C9h
Z80_OPCODE_RST30 equ 0F7h
EXPTBL equ 0FCC1h
SLTTBL equ 0FCC5h
H.RUNC equ 0FECBh
H.STKE equ 0FEDAh
org 4000h
dw 4241h
dw init
ds 4010h-$,0
init:
; return if mirrored on 8000h
ld a,h
or a
ret m
call setupregs
; ; return if H.STKE is already hooked.
; ld a, (de)
; cp Z80_OPCODE_RET
; ret nz
; return if H.RUNC is not hooked. (DOS is not initialized yet)
ld a, (hl)
cp Z80_OPCODE_RST30
ret nz
; save original H.RUNC to H.STKE
ldir
; ld a, Z80_OPCODE_RST30
; ld (H.RUNC+0),a
call getslotp1
ld (H.RUNC+1),a
ld hl, H.RUNC_handler
ld (H.RUNC+2),hl
; ld a, Z80_OPCODE_RET
; ld (H.RUNC+4),a
ret
H.RUNC_handler:
call setupregs
push hl ; push H.RUNC
push de ; push H.STKE
; restore original H.RUNC from H.STKE
ex de,hl
ldir
; clear H.STKE
pop hl
ld (hl), Z80_OPCODE_RET
; chain to original H.RUNC
ret
setupregs:
ld hl, H.RUNC
ld de, H.STKE
ld bc, 5
ret
; [input] none
; [output] a:selected slot state of page1
; [work] hl,bc
getslotp1:
; get primary slot state
in a, (0a8h)
and 00001100b ; page1 mask
rra
rra
ld c, a
add a, low EXPTBL
ld l, a
adc a, high EXPTBL
sub l
ld h, a
ld a, (hl)
and 80h ; bit7:1=slot is extended,0=not
or c
ret p
; get extended slot state
ld b, a
ld a, c
add a, low SLTTBL
ld l, a
adc a, high SLTTBL
sub l
ld h, a
ld a, (hl)
and 00001100b ; page1 mask
or b
ret
ds 6000h-$,0FFh
Normally, to use a hook, we have to copy the current hook somewhere in RAM when it's already in use, then place a new hook that calls it a routine that calls the moved hook and the routine you want to call by the hook. (I do not know if I'm clear)
