Category: schematics

Programmable Deactivation of MONITOR ROM for Sord m5

The Sord M5 computer has a basic configuration with only 4kB of RAM, which can be expanded to 32kB using an additional cartridge EM-5. By making a small modification to the computer, the memory can be expanded up to 64kB by deactivating of the MONITOR ROM, which occupies the address space 0000-1FFFH. This modification opens up new possibilities for the computer, such as running MSX or ZX Spectrum emulators or CP/M, and so on. This modification is not something new, it was already realised in the 1980s. The modification itself involves interrupting the connection between pin 15 of the GA15 chip and pin 20 of the IC21 ROM memory , and inserting a resistor with a value between 330-390ohm, as shown in the picture. This weakens the signal from GA15 and allows for external control. The computer's functions remain unchanged by this modification, but various RAM DIY modules, including FlexiCard, can deactivate the MONITOR ROM by setting log. 1 on ROM0 bus signal.

New schematics

I've added few more schematics recently, for which I thank Roman Štec, who gave them to me, and also the author Jindřich Stuchlík.

  • FD-SIO-EM64
  • SIO

I've also added new redrawn FD-5 schematic and 2 block designs of Sord

You can find them here

Sord m5 related schematics


Here I'm gonna place DIY guides and schematics related to the Sord hardware. Not so much now but maybe during the time another will appears....