>yesterday i managed to get really frustrated with my MSX as
>it would keep corrupting my floppies and give me lots of
>errors. I was writing to addresses E000h -> EFFFh... My
>assembler/basic books 'told' me that was correct after using
>a "CLEAR 200,&HDFFF".. WRONG!
Your books could also have told you that this address
space is used by DiskBASIC for storing drive parameters...
>It seems my external diskdrive controller cartridge (is this
>how you name it? :) reserves about 3kb of memory IN THAT
>AREA.. and i kept wondering why my floppies went banana's
>all the time.
DiskBASIC reserves about 1K (IIRC) per logical disk
(which can be more than the number of physical disk drives)
for storing drive parameters and stuff at the top of the
available RAM space, which starts just below the first
system variables. You can make this occupied space smaller
by pressing [CTRL] at startup. The diskROM will
then only reserve 1 block, so you can only access 1 drive
per diskROM. This is totally legal and documented
diskROM/diskBASIC behaviour. Sorry.
(Manuel! Is this a topic for the FAQ?)
>Soo... is there a way to see where ROM's are placed, so you
>can work around them? My current fix is to let basic start
>at 9000h and use 8000h->8FFFh for my own stuff (this is
>probably the most simple way, as it gives me a static
>address i can work with, but it also adds some
>'start-overhead' as i have to poke some values and then NEW
>to let basic start at 9000h).
The exact address of the start of the RAM area used by
the diskcontrollers _can_ be calculated from (a lot of)
system variables, but it's easier to just assume that
everything beyond $D800 is hazardous and start your ML
programs at $C000 or $D0000, depending on the size of the
ML and/or BASIC you need. Relocating BASIC, like you did
is also a possibility.
HTH,
Eric
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