MicroBee

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Microbee standard logo and company logotype

Microbee Premium Series 128K

A complete Microbee system.

MicroBee (Micro Bee) was a series of home computers by Applied Technology, later known as MicroBee Systems.

The original MicroBee computer was designed in Australia by a team including Owen Hill and Matthew Starr. It was based on features available on the DG-Z80 and DG-640 S-100 cards developed by David Griffiths, TCT-PCG S-100 card developed by TCT Micro Design and MW6545 S-100 card developed by Dr John Wilmshurst. It was originally packaged as a two board unit, with the lower "main board" containing the keyboard, Zilog Z80 microprocessor, Synertek 6545 CRT controller, 2K of "screen" RAM, 2K of character ROM (128 characters) and 2K of PCG (Programmable Character Graphics) RAM (128 characters). Each byte in the screen RAM addressed a character in either the character ROM or PCG RAM. A second board, termed the "core board", contained the memory, and on later models also included a floppy disk controller.

1 Kit beginnings
2 The IC model
3 Disk machines
4 Colour
5 The Premium Series MicroBee
6 Games
7 Final versions
8 External links

[edit] Kit beginnings

The computer was conceived as a kit, with assembly instructions included in Your Computer magazine, in June 1982. After a successful bid for the New South Wales Department of Education computer tender, the computer was repackaged in a two-tone beige and black case, and sold pre-built. The 16kB ROM held a 'DGOS' (a cassette interface and loader), the MicroWorld BASIC interpreter written by Matthew Starr, and an optional Z80 editor/assembler written by Ron Harris.

Original MicroBees ran at a clock speed of 2MHz, with a video dot clock of 12MHz, which was sufficient to display 64x16 characters (512x256 pixels) on a modified television or composite monitor. The original machines were supplied with 16 or 32K of static RAM, and stored programs on cassette, using Kansas City standard and 1200 Baud encoding.

[edit] The IC model

The IC model was released in 1983, increasing the clock speed to 3.375MHz, and allowing (through use of a 13.5MHz video clock) display of 80x24 characters (640x264 pixels), again on a modified television or composite monitor. It also included a 4K "Telcom" terminal emulator ROM.

[edit] Disk machines

A floppy disk based machine was also released in 1983. Early disk machines used 56K of static RAM, with a 4K BIOS ROM. They ran CP/M 2.2. The disk controller, based on the Western Digital WD1793 Floppy Disk Controller chip was contained in an add-on card that connected to the core board. The machines used 5.25" floppy disks.

Dynamic RAM disk machines with 64 or 128K RAM followed soon after, with a WD2793 Floppy Disk Controller incorporated on the core board. Later disk machines used 3.5" floppy disks.

[edit] Colour

A colour machine was also released in 1983, called the "32K Personal Communicator". This added a second byte of RAM for each character position, allowing each character to have 2 colours from a palette of 16. The extra circuitry was contained on an additional board mounted under the main board, with numerous messy connections to the main board.

[edit] The Premium Series MicroBee

In 1985, a new mainboard was introduced. The resulting machine was called the "Premium Series" model. The new mainboard had 8K of screen RAM, 8K of "attribute" RAM (raising the possible number of PCG characters to 32,768), 8K of colour RAM, and up to 32K (16K installed) of PCG RAM. 16K PCG RAM was sufficient to allow full 512 x 256 bit mapped displays with a limited colour palette. These machines were typically sold with dual-floppy drives (or a 10MB 'Winchester' disc) held in a monitor stand that connected to the main unit.

[edit] Games

Many memorable games were written for the Microbee, including:

Microspace Invaders
Robotman - a Pacman clone
Asteroids
Hoards of the Deep Realm
Emu Joust - a Joust clone,
Kilopede - a Centipede clone,
Ghost Muncher - a Pacman clone
Wumpus

As well, numerous adventure games were written, mainly in BASIC, plus educational software.

[edit] Final versions

The final version of the MicroBee, released in 1987, was the 256TC. This increased the memory to 256K of dynamic RAM and had a new keyboard with numeric keypad.

MicroBee Systems also designed a PC clone, called the "Matilda", or 640TC, which ran an NEC V20 chip, and emulated the MicroBee CP/M systems in software.

An advanced next generation model code named "Gamma", was based on the Motorola 68000 and Zilog Z80 processors was designed but never made it to the market.