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Old 5th May 2019, 12:36 am   #16
Join Date: Aug 2009
Location: Worthing, Sussex, UK.
Posts: 514
Default Re: Gemini 80-Bus System

Within the BIOS there is a Disk Parameter Header for each disk drive.

The SELDSK routine within the bios gives the address of the disk parameter header. (DPH)

The disk parameter header gives references to several ram areas - one of these is the DPB for the drive. DPBs can be shared between drives, but DPH must be unique per drive.

The DPB contains numbers that define the layout of the disk. The diskdef program will calculate these numbers for you from the disk layout. Actually the diskdef program is part of my multi format system which will allow the gemini to read most floppy disk formats. Now you have xbeaver running
you should have them.

Note to run it type the following

killvpmm - this kills the virtual multitasking software and returns to CPM - actually CCPZ/BDOSZ
mfb - this installs the multi format system

and then use diskdef as required to install different floppy disk formats to drives N, O and P.

If you don't want to use the CP/M filesystem you can load mfb within VPM/M

? gives help witin diskdef, but it works like a spreadsheet.
JohnBHanson is offline   Reply With Quote