Aamber Pegasus

[2][3] An optional multi ROM board in conjunction with a rotating dial allowed switching between 6 EPROM banks containing multiple language environments, games and applications.

[6] Especially the networking version attempted to address the New Zealand Government's computers in schools initiative,[7] but never produced the hoped-for large orders.

One of the most unusual aspects of the machine is that to save the cost of a CRTC, the processor set up some bits on the 6821(PIA) to control the row being read out, then stepped through a series of NOPs so that the address lines of the CPU could act as a big counter.

At the end of the screen the output is blanked, and the CPU gets to do some “real” work until the FIRQ pin is pulsed by the 50 Hz line from the power supply.

Because of this, the CPU is ~90% occupied as a counter, so in a non-real-time application you could disable the FIRQ (one bit in the 6809's CC reg) and the Pegasus ran ~10x faster – albeit with a blank screen.

Aamber Pegasus PCB with MONITOR 1.0, FORTH 1.1A and FORTH 1.1B EPROMs installed