Western Digital is now best known as a disk drive manufacturer, but their origin was as a semiconductor company. At one time Western Digital was the leading manufacturer of calculator chips. Western Digital also developed the first single-chip UART, in conjunction with DEC, and their other popular computer-related products included the 177x, 179x, and 279x floppy disk controllers.
In the mid-1970s, Western Digital designed an NMOS microcoded 16-bit processor chipset for the DEC LSI-11. With different microcode, and an instruction set that was similar to but not binary-compatible with the PDP-11, the chipset was offered as the WD16, and used by Alpha Micro in S-100 bus systems.
When UCSD Pascal started becoming popular, Western Digital developed a set of microcode to directly interpret p-code. The Pascal Microengine was made available in several forms:
Third parties built other systems using the Pascal Microengine, including:
The Pascal Microengine uses release III.0 of the UCSD p-system, which is not used on any other platform, though it is fairly similar to IV.0.
Pascal Microengine documentation is available from Bitsavers, courtesy of Al Kossow, Software Curator, Computer History Museum, and Jos Dreesen:
Pascal Microengine software is available from Bitsavers, courtesy of Al Kossow, Software Curator, Computer History Museum:
I've designed a floppy disk adapter board for the WD-900 and WD-90, which use a DC-37 connector for the floppy disk port.
I've dumped and disassembled the microcode and PLAs and am working on a simulator.
Last updated February 7, 2016
Copyright 2016 Eric Smith
