Pascal MicroEngine

The Pascal MicroEngine was a series of microcomputer products manufactured by Western Digital from 1979 through the mid-1980s, designed specifically to run the UCSD p-System efficiently. Compared to other microcomputers, which ran a machine language p-code interpreter, the Pascal Microengine had its interpreter implemented in microcode. So, p-code was, effectively, its native machine language.

The most common programming language used on the p-System is Pascal.

The MicroEngine ran a special release III p-System, which was not to be used on any other platforms. However, the enhancements of release III were incorporated into release IV which was made available for other platforms but not for the MicroEngine.

The MicroEngine series of products was offered at various levels of integration:

The MicroEngine chipset was based on the MCP-1600 chipset, which formed the basis of the DEC LSI-11 low-end minicomputer and the WD16 processor used by Alpha Microsystems (each using different microcode).

One of the well regarded systems was the S-100 bus based dual processor cards developed by Digicomp Research of Ithaca, NY. These cards deserve an entry on their own, as they survived the demise of the WD single-board system and delivered reliable performance at up to 2.5Mhz. A typical configuration was a Digicomp dual processor board set, containing a Zilog Z80 and a bipolar memory mapper harnessed to a microengine chipset on the second board, linked by a direct cable. The sole configuration known to be still running in 2013 and documented on the web is described by Marcus Wigan and contains 312 kB of memory, RAM disc support through a modified Z80 BIOS (written by Tom Evans) taking advantage of the memory mapping chip on the Z80 board, and using the UCSD Pascal III version if the operating system tuned specifically for the awD chipset - once the Microengine had booted the ram-disc was available. A software facility within UCSD Pascal allowed the system to copy the entire operating system to the ram disc and transfer control to it. This sped it up remarkably. This use of a Z80 BIOS to handle all the devices, allowed the use of a range of floppy discs, I/O boards and hard disk controllers .

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