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Old 17th Jun 2019, 10:34 am   #99
john_newcombe
Hexode
 
Join Date: Apr 2019
Location: Skipton, North Yorkshire, UK.
Posts: 252
Default Re: Gemini 80-Bus System

In the meantime I have been re-reading and re-reading the posts in this thread and the good news is that I am really starting to get my head around the bios changes required to get the 80 track disks incorporated.

I have been looking at the source code and can see that to support the GEMQDDS 80 track format I need to change a couple of Equates. This recalculates the tables correctly (scheme b) and sets the CHK and ALL buffers to the correct sizes. I now understand how to build the bios using .org/.phase etc. and that I have to transfer the resultant multi.com to the relevant portions of the disk.

Doing it this way seems the most natural and would support any Gemini disks should they ever turn up, however, this also would cause a block size change to 4k.

From this point I have two routes, my A: drive is a Gotek and I can manipulate the disk images in anyway I need, assuming I know what I need. My B: drive is a physical 80 track 5.25 drive which has already been used to format disks at 35 tracks (from RP/M) using the Format.com you sent me (it is not possible to format an image on the Gotek).

I have yet to research how the change in block size affects the disk format.

I am thinking that if I can get a suitable disk format utility (perhaps there is one on Tony's hard disk or in the public domain), I could format a physical disk in B: and then make an image of that. I could then easily add CP/M (with the new bios) on to the system tracks.

But... there is probably a better way.
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