The Elen Computer was constructed in an aluminum 19 inch rack during 1991/2. It was based on a Motorola 68030 processor clocked at 33MHz with 4 MByte of DRAM.

The operating system was written in C using a C compiler that had been bootstapped with the BCPL compiler running on Stallone. It provided virtual memory with demand paging and was posix-like in most ways. It was basically a homebrew linux running on homebrew hardware.

A pair of 3 inch, double density floppy drives were provided and these connected with an IDE bus to the main IO card.

A 3.5 inch, 50 megabyte IDE disk drive served as the main store.

I/O was via a pair of serial ports, a parallel port and two sets of MIDI connections.

The I/O card provides serial ports, a pair of IDE interfaces and a real time clock.

Back Panel I/O

Rear view, showing a pair of MIDI ports and a pair of RS 232 serial ports. One midi port was used for time code and transport control whereas the other was used for instruments.

Internal Hardware Views

General view inside the box. Switched mode power supply at bottom.

Internal view of back panel, with MIDI opto-isolators in card insulator.

The computer was implemented on two pieces of veroboard joined with a 60 way cable.

The top view of the CPU card with 68030, boot EPROM and SIMM memory. The SIMMs were soldered in, not socketed. Most of the logic was implemented in PALs.

Underside of the CPU card.

The IDE-connected floppy drive controller. A digital PPL implemented in a 22V10 PAL was used for clock recovery.

The hard disk drive, 50 Mbyte Seagate IDE.

The I/O card, containing UARTS, NV RAM, real-time clock.

(C) 2005 DJ GREAVES. UP.