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My CP/M V2

A project log for My CP/M Version 1A

I decided to do a minor upgrade to My CP/M (Version 1). Swap RST6.5 for RST7.5 and increase the FRAM disk capacity from 32k to 256k.

agp.cooperagp.cooper 07/10/2020 at 11:430 Comments

My CP/M V2

Should not really be working on this now, but anyway I updated cbios.asm for the W29C040-90B 256 byte page size. It was not that hard really, you just read to a buffer the"other" segment (that is within the 256b page boundary) and then write back the buffer before (immediately) writing the target segment.

I also had the rework the disk/track/segment address from: 

  DDTTTTTT 1TTTTSSS SAAAAAAA

to:

  DDTTTTTT 111TTSSS SAAAAAAA

where:

D = Disk

T = Track

S = Segment

A = Address of a byte withing a segment.

The first address format (V1) could access 32kb RAM, 4 disks of 2 Mb capacity while the second (V2) can address 56kb RAM, 4 disks of 512kb capacity.

In theory, CP/M can access 16 disks of 8 Mb capacity.

Alan

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