problem with msx-dos:
I found a .rom file of 64KB in size. It starts with 'ab' so it should be mapper from offset 0x4000
but then I have 16KB which won't fit
where do I map that?
or must i split it in half and then use 2 slots?

I tried splitting in half (since at offset 32768 there's also the 'AB' marker) but then it goes into an infinite loop doing nothing. i also mapped the disk i/o ports to both slot 1 and 2 (the slots in which i put the roms) but that didn't help either

also; will all msx-dos version also run on msx-1? or do i need msx-2 for that? or is there an msx-1 version if required?

Mappers use bankswitching.
- http://en.wikipedia.org/wiki/Bank_switching
- http://bifi.msxnet.org/msxnet/tech/megaroms.html

MSX-DOS prior to version 2 works on MSX1 too.
(there's no MSX-DOS1 ROM btw, it only needs MSXDOS.SYS and COMMAND.COM on the disk to boot)

With some sort of bootsector i assume?
Does anyone have a .dsk-file with msx-dos1 for me?
none could be found at msxarchive.nl

I copied msxdos.sys and command.com to a blank disk-image, then loaded the emulator with the msx disk bios rom inserted but all I get is:

MSX BASIC version 1.0
Copyright 1983 by Microsoft
23432 Bytes free
Disk BASIC version 1.0
Ok
callsystem
Illegal function call
Ok

is what your emulate system comprises a disk controller because it n' there d' does not have origin on a MSX1

Check first, that your disk bios ROM is compatible with the controller you are using and that the controller is connected to correct memory address or I/O space.

If you have PC bootsector your MSX usually hangs on boot. If you format the disk with CALL FORMAT command it will definately install valid MSX-bootsector.

The disk bios rom is compatible as I can read/write files as well as list the contents of a disk.
I verified with openmsx (philips vg 8020 + philips vy 0010 and the disk image at http://keetweej.vanheusden.com/~folkert/md1.zip) that my image runs so something is fishy indeed with my emulator. Well, still 2 days vacation left

Problem solved!
I was using the disk.rom-file from fMSX which seems to do things that do not work with my emulator. Have to invistigate later on what it is. Anyway, with an other diskrom (FSFD1.ROM) it all runs fine AND boots msx dos 1! So now I can run zexall!
Thanks for all the help people!

IIRC fMSX uses not existing Z80 commands to trap disk routines to emulator. Check that there is no weird stuff on #4010 or directly after jump.