The machine was based around a
Z80A CPU clocked at 4
MHz (6 MHz for the 128/192 KB models) and featured a
Motorola 6845 as
video controller. It was possible to run
CP/M with the optional 5.25"
floppy disk-drive on the 96 KB and 128 KB models. Unique features of this computer (compared to other home computers at the time) include: • All numbers were floating point BCD numbers (even line numbers). • The computer always ran in "high" resolution graphics mode (256x252 pixels in eight colours) using a 6 x 10 pixel font. Only a few bytes of graphic memory could be manipulated during the
horizontal sync period, and thus graphics were extremely slow compared to most other computers. • Up to 192 KB of RAM and 20 KB of
ROM (16 KB on the smallest model) on a 16-bit
address bus was implemented using special hardware. As a consequence, certain RAM areas shadowed by ROM could only be used for data storage and the video memory had a green and alternative green bank that could be switched by a
hardware register. • For sound it had a simple (6-bit)
DAC. A
comparator was included to serve as an
ADC (primarily used for reading from
tape drives). Compared to, for example, the
Commodore 64, the
BASIC was more extensive and faster and the resolution of the graphics was better; == History ==