Re: Lisa GEMDOS

gilles wrote:
> The main problem
> is that when you run on atari, you create discs using atari GEMdos so
> in final atari disc geometry (ie mostly msdos).
> also such discs don't have the tags (only 0xAAAA type tag of first
> sector may be necessary to boot).
> To make boot disc for lisa we need to:
> _ define correct gemdos lisa disc geometry.
> _ create a disc image with this geometry and gemdos lisa binary (that
> seems to be present in the archive)
You can easily create disk images using lisafsh-tool from hex text files. Feed it the appropriate commands and it'll produce the disk copy 4.2 output.

You'll need to put the boot sector for Lisa on it, if one was provided, otherwise write one to load the Lisa binary. If one was provided, disassembling it would give you a hint of where on the disk it wants that file.

So that means you'd need to guess what the CP/M68K layout for the CP/M file system is and build a disk that will work on the Lisa. The file system should be pretty straight forward.

If the ST Geometry isn't too different perhaps you could convert it to what you think it would look like in a 400K disk and the boot sector can be hard coded to load that lisa binary.

Unless they changed things for CP/M68K, this should help:

"the disk drive as an entity with a number of tracks, each containing a number of 128-byte records. In the early days, a record equalled a sector - both being 128 bytes of storage. But later on, sectors became larger and disks got more double-sided. Hard disks even got up to 4 platters with 8 sides to write on. The BIOS hides this physical reality from the rest of CP/M and translates standard tracks and records into whatever is the physical layout of the disk."

from: http://www.dcast.vbox.co.uk/cpm.html

This also has the layout of the file system.

So geometry wise, you'd take the Lisa's 800 512 byte blocks and chop them up each into 4 128 byte sectors, perhaps skipping the boot area, (or not?).

Note that you'll need to guess what the blocking factor is and there can be no more than 256 blocks per disk. So 800/256=3.1 so either we use 3 or 4 - likely 4.
Hope the ST has the same values, otherwise you'll need to redo all the directory entries since they also contain block #'s instead of just sector #'s.

Hopefully whatever you see on the ST will apply exactly - just with more/less sectors - from what I see on the web the ST supports either 360K or 720K floppies (1.44M later as well, but let's not make life harder), so if you can force the target drive on STEEM Engine to be 360K, it should be close enough to the Lisa's floppy to match the block size to sector translation.

So if you can get a disk dump from the ST emulator with the Lisa boot files on it, strip off the ST boot blocks and replace them with a Lisa boot sector that says load this binary at this address and execute (you can probably steal this from LOS as it has a simple one that loads the boot loader), you can then feed the whole thing to lisafsh-tool as hex text with the write commands, set sector 0's tag 4,5 to AA,AA and you'll have a bootable Lisa CP/M 68K. (Assuming the driver files are real ones, that Lisa driver needs to provide the same functions of the physical machine BIOS to the BDOS.)

Once you have the CP/M boot disk, you can repeat and copy the rest of GEM by copying its files over to the same or 2nd disk.

Would be interesting to see what it does with PIP A:*.* B: - if it goes into a loop asking you to swap floppies or not. :-)

Best of luck.

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