On Tuesday 13 March 2001 13:07, you wrote:
> Unfortunately, that command doesn't help me much here. The problem is that
> cartridges use whatever video mode is active when they are booted.
> Therefore, even though the cartridges were written for NTSC televisions,
> they boot in PAL on my NTSC television. I was hoping for a way to boot
> directly to cartridge after I've done vdp(10)=0, so that the 60Hz mode
> would be conserved; in the softboot, the screen merely returns to 50Hz as
> it boots up again.
Maybe you can modify the BIOS ROM to boot in 60Hz by default. Does anyone
know how easy/hard it is to replace the 8250 BIOS by an EPROM? It was done
for MSX2 to MSX2+ expansions, so it's possible.
Another option is to build a switch on your cartridge port, to enable/disable
slot select. Although an 8250 is pretty resilient against inserting
cartridges when power is on, it's not something you should do on a regular
basis. Using a small machine code program, it's possible to boot most
cartridges (only cartridges that use the disk drive fail, like King's Valley
2 and Metal Gear 2).
The program looks like this:
(programmers, please verify it)
SLOT: equ 1 ; Cartridge slot containing ROM
org #C000
; SCREEN 2 - avoid display problems on MSX1 ROMs
ld a,2
call #005F
; select ROM in page 1 and 2
ld a,SLOT
ld h,#40
call #0024
ld a,SLOT
ld h,#80
call #0024
; get start address and jump there
ld hl,(#4002)
jp (hl)
Bye,
Maarten
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