] 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.
This is indeed the best option. It's a bit in the BIOS ROM that decides if
the computer must start in 50 or 60 Hz mode. Though, I do not remember the
address.
] 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)
OK, Here I go
]
] SLOT: equ 1 ; Cartridge slot containing ROM
] org #C000
OK
] ; SCREEN 2 - avoid display problems on MSX1 ROMs
] ld a,2
] call #005F
Not correct. Should be screen 1. MSX is normally in screen 1 when starting a
cartridge. And to be entirely save, screen 0 should first be switched to 40
column mode. Just in case that it is a MSX1 cartridge that switches to screen
0 but does not modify the width of the screen.
] ; select ROM in page 1 and 2
] ld a,SLOT
] ld h,#40
] call #0024
OK
] ld a,SLOT
] ld h,#80
] call #0024
Not needed. Cartridge will select ROM in page 2 itself if necesary.
Otherwise, cartridge may expect RAM to be present in page 2 (at least, MSX2
cartridges).
] ; get start address and jump there
Too early. You must first reset variables in workarea related to floppy work
area. E.g. the interrupt hook pointing to diskrom should be reset. There are
also a few other variables to be reset in workarea but I do not recall them
by heart. However, they can be found in any disk version of games that where
originally published on cartridge.
] ld hl,(#4002)
] jp (hl)
OK
Kind regards,
Alex Wulms
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