Editing MicroBee (section)

== Ancestry ==
The microbee was the integration, simplification and modernisation of the following S-100 cards sold by Applied Technology, Microworld BASIC and DGOS Monitor for their System Z.A.T. chassis.

* DG680 CPU - Z80 Single board Computer designed by David Griffiths
* MW640/DG640 VDU  - Visual Display Unit designed by David Griffiths. (The DG640 VDU was itself was based upon the Processor Technology VDM-1.)
* TCT-PCG  - Programmable Character Generator for the DG640 VDU designed by Craig Barratt
* MW864 - MEGAMEMORY  64K [[Static RAM]] Memory board designed by Owen Hill
* MW2516  - 16K ROM 16K ROM Card designed by Owen Hill
* MW6545 - User Programmable VDU designed by John Wilmshurst

The removal of the S-100 bus support and configuration hardware and some other features made the microbee much simpler and cheaper than its ancestors.

Examples:

# The VDU Attribute RAM of the DG640 VDU was not employed in the original microbee (but was reinstated in a modified and extended form for the Premium Series Microbee)
# Z80 CTC (Counter Timer Counter)
# Tape motor on/off control
# 8 bit input sense port
# Configuration [[DIP switch]]es

The utilisation of higher density memory devices made also the microbee smaller. HM6116 (2K x 8 bit) were instead of the earlier 2101 (1K x 1bit) and 2114 (1K x 4bit) static RAMS and 2732 (4K x 8 bit) ROMs instead of 2516 (2K x 8) ROMs as program ROM.  Subsequent models used the even denser HM6264 (8K x 8 bit) static RAMs, 4164 (64K x 1 bit) dynamic RAM and 27128 (16K x 8 bit) 2764 (8K x 8) program ROMs.