Consisting initially of a Z80 platform for running machine code that in the early days had been tested using the SLAVE system. This system (Processor 1) was modified to run either the Level 2 Bootstrap or the 8Kb version of the ETI Forth Card mounted in slot 2.
Later, a card mounted ZX81 was fitted into the same RACK in slot 15, it had
four backplane connectors on it's buss. This particular ZX81 ran only the
SKYWAY FORTH and one of the connectors was used to interface the RAM cassette
card allowing the use of Planet cassettes and an I/O port.
The tape input port was modified to accept TTL voltage level input signal to
allow the Spectrum Forth File Server to be connected.
To the right in slot 18 is the ETI SBC-Forth system.
Shows ZX81 Skyway Forth with RAM cassette interface, on the left of this picture. The
right hand PCB's are the ETI SBC Forth System
Shows the full Rack, a total of three Z80 based systems.
were salvaged from a LAN system. They where the forerunner to flash memory cards. Of Racal Milgo manufacture they consisted of a plastic case about the size of a pack of twenty cigarettes. Inside is a PCB on which there is mounted a battery and either three 2kb RAM chips (Toshiba 6116) giving 6Kb total storage or two 8Kb RAM chips (type 6164) giving 16Kb. The circuit board protruding from one end allowing it to be plugged into a suitable connector.
The SLAVE system was developed when the main processing ran on a ZX81 that was built into a case that supported additional memory/eprom and I/O cards. It also had a second processor that functioned as a slave to the ZX81.
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