ROM Program for Microcomputers (RP/M) was installed in Gemini GM811 and GM813 processor cards where disks were not used. It was a 4kB monitor with similar functions to Nascom’s NAS-SYS, however the programming interface was virtually identical to CP/M. All software developed using RP/M could be run on CP/M systems and some CP/M software (e.g. MBASIC) would run on a diskless system if it was loaded from tape or an EPROM! The first version was 0.1 which had no reported bugs! However, version 2.0 was released in June 1982 to cope with the “new” 80-track floppy disks and the GM813 processor card. It still had no reported bugs!

RP/M had a distinct difference from Nas-Sys. It was located at address 0F000 and expected RAM from address 0000. In this respect it was much closer to CP/M.

On initialisation or Reset RP/M would first search for a floppy disk drive and attempt to boot the system from it. It did not support hard disk drives.

Version 0.1

I still need information on this version.

Version 2.0

Main additional features over version 0.1

  • The boot routine works with both Pertec DD/DS and Micropolis DD/(SS or DS) double-tracking drives
  • Operates with both GM811 and GM813 cards
  • Automatic disk boot on power-on or reset if a disk card is in the system
  • Operation is possible without a video card, using the serial port
  • Support of parallel printers is included
  • Screen edit now invoked with Control-@ instead of DEL for compatibility

Version 2.0 RP-M manual

Version 2.1

No, this wasn’t a version increase because of a bug!
The hardware recognition was changed to allow correct operation of a system comprised of a GM811 processor, RP/M 2.0 and a MAP 256kB RAM card. This was caused by the memory addressing ports chosen by MAP.

There was no official version numbered 2.2 to avoid confusion with CP/M version 2.2.

Version 2.3

Boot command has been changed to allow an optional argument:

  • B
  • Boot drive A, double density, sector 0, 5-1/4″  (same as previously)
  • B sscd   where sscd is a single hexadecimal value, leading zeros can be omitted
  • ss is the physical sector to be read. Normally 0 or 1
  • c is the command digit 0=5.25″ DD  1=5.25″ SD  3=8″ SD
  • d is the drive select digit 1=drive A  2=drive B  4=drive C  8=drive D



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