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Old 13th May 2019, 11:27 pm   #31
Join Date: Aug 2009
Location: Worthing, Sussex, UK.
Posts: 516
Default Re: Gemini 80-Bus System

Just disassembled RPM V2.2 and it reads sector 1 at address 80h and then jumps to address 82h. And also looks for the first two bytes being G8 - clearly this is for a different type of CP/M system

To Patch RP/M to boot your system

The following might be helpful to add into your config file
binload 0xf000 ~/beaver/RPM_2.2.ROM
#Patch top of ram for RPM
byte 0f0a8 21 00 f0
#select boot sector
byte 0fc36 0
#patch disk code GG for floppy boot id
byte 0fc59 47 47

#patch in jump to patch routine
byte 0fc72 e0 ff

#patch routine - copy sector from 80h to 0h
byte 0ffe0 21 80 00 11 00 00 01 80 00 ed b0 f3 c3 02 00

( And still include the line )
byte 0000 c3 00 f0

This should boot the disk .

NOTE If you are doing a ROM do not patch the top of RAM test. This is done on xbeaver because actually xbeaver does not support ROM. If not patched the memory size routine overwrites the RP/M code.
JohnBHanson is offline   Reply With Quote