Pascal MicroEngine

The Pascal MicroEngine was a series of products manufactured by Western Digital from 1979 through the mid 1980s, designed specifically to efficiently run the UCSD p-System. Whereas other microcomputers 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.

As usual on the p-System, the most common programming language used was Pascal.

Notable aspects

One of the first validated Ada compilers (MicroAda) was developed on and for the MicroEngine; this was the only other programming language available The March 1979 Preliminary Edition of the reference manual stated that a BASIC compiler was available for the system, but it is unknown if this compiler ever actually shipped.] . "A(da" replaced "A(ssmble" on the main command menu, as no native assembler was available or needed. Due to limited memory (62K 16-bit words, the last 2K words being reserved for memory mapped input/output and PROM for the harddisk boot code) only very small Ada programs could be compiled. At one point in the compilation the compiler swapped the operating system out to disk, to gain just a little more room.

The MicroEngine ran a special release III p-System, which was not 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:

* WD-9000 five chip microprocessor chip set
* WD-900 single board computer
* WD-90 packaged system
* SB-1600 MicroEngine single board computer
* ME-1600 Modular MicroEngine packaged system

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 AlphaMicro (each using different microcode).

Reception

At the time of introduction, the only competitors were 8-bit processors (mainly 8080, Z-80, and 6502 based systems). The MicroEngine could compile Pascal source code in a fraction of the time (typically about 1/10) required by contemporaries. Fast compilation made the MicroEngine especially nice as a developer's machine. This performance advantage was eroded by the later availability of p-code to native machine code translators, and mainstream 16-bit microprocessors such as the Intel 8086 and Motorola 68000.

When first announced the MicroEngine accumulated a very large number of pre-orders (for the time). The first boards shipped were poorly designed (power and ground traces the same size as signal traces, very few capacitors), required a large number of modifications, and even then did not work reliably.Fact|date=December 2007 A couple years would pass after introduction before a well-engineered MicroEngine was available. Between a damaged reputation and the introduction of the IBM PC, in the end the MicroEngine was only modestly successful.

One example of a commercial product based on the MicroEngine was the AVAB Viking lighting control system, which used the Modular MicroEngine boards along with some custom hardware.

ee also

*Pascal programming language
*UCSD Pascal
*p-code machine

External links

* [http://web.archive.org/web/20060925004324/www.machine-room.org/companies/303/ Western Digital Pascal MicroEngine]
* [http://www.bitsavers.org/pdf/westernDigital/WD90_Pascal_Microengine/ Pascal MICROENGINE documentation] at bitsavers.org

Notes