MicroBee

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:

1. 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)
2. Z80 CTC (Counter Timer Counter)
3. Tape motor on/off control
4. 8 bit input sense port
5. Configuration DIP switches

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 more dense 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.

The computer was released as a kit, with assembly instructions included in Your Computer magazine, in February 1982.[2] 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 16 kB ROM held the MicroWorld BASIC interpreter written by Matthew Starr and DGOS (David Griffiths Operating System) compatible System Monitor. In addition to the 16 kB ROM, there is additional ROM socket for optional programs such as WORDBEE (Word processor) or EDASM (a Z80 Editor/Assembler that was written by Ron Harris).[3]

Original MicroBees ran at a clock speed of 2 MHz, with a video dot clock of 12 MHz, which was sufficient to display 64 × 16 characters (512 × 256 pixels) on a modified television or composite monitor. The original machines were supplied with 16 or 32 kB of static RAM, and stored programs on cassette, using 300 or 1200 Baud encoding.

The IC model was released in 1983, increasing the clock speed to 3.375 MHz, and allowing (through use of a 13.5 MHz video clock) display of 80 × 24 characters (640 × 264 pixels), again on a modified television or composite monitor. It also included a 4 kB "Telcom" terminal emulator ROM.

A complete MicroBee Computer-In-A-Book system

A floppy disk based machine was also released in 1983. Early disk machines used 56 kB of static RAM, with a 4 kB 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 uses 5.25" floppy disks.

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

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. The foreground colour has 32 possible values (5 bits) and are determined by the contents of the 82S123 PROM located on the colour board. Not all foreground colours combinations are unique with only 27 being possible. The background colours were made up from the remaining 3 bits of the colour RAM byte (8 colours) and another 3 bits on a colour control port that controlled the RGB background intensity level. This allowed the intensity of each of the RGB colours to be set to full or half intensity but only 7 different values could be in effect at any one time and changing the intensity value would affect the entire display. The extra colour circuitry required an additional board mounted under the main board, with numerous messy connections to the main board.

The Premium, 256TC and Teleterm models released in 1986 incorporated colour on the main board and used a different colour design compared to the earlier model and was not compatible for the resultant colours that were produced but application and system software will work on either hardware designs. The later colour design was largely compatible with the Color Graphics Adapter used on the IBM PC where 4 bits were used for the foreground and another 4 bits for the background colours.

The B-ETI was a Microbee-based serial terminal. It could emulate either an ADM-3A or Televideo 912 terminal. The display format was monochrome 80 × 24 and it supported communication at either 300 or 1200 baud. An advertisement for a "special introductory offer" with an asking price of A$275 appeared in the December 1983 issue of Electronics Today International magazine.[4]

Introduction, BETI Users Guide:

The BETI was designed as a low cost serial terminal operating at speeds of up to 4800 baud (1200 baud without handshaking). The BETI also provides optional automatic code conversion to and from the baudot 5 level code used for RTTY and TELEX applications.

Specifications:[5]

• Codes supported: US ASCII and CCITT BAUDOT.
• Baud rates: 45.5, 50, 75, 110, 300, 600, 1200, 2400, 4800.
• Default settings: 4800 baud US ASCII full duplex.
• Emulation: ADM-3A and TVI 912C (except for attributes).
• RS232 port: Configured as DTE with 0-12V swing.
• Parallel port: Connects to Centronics printer with adapter.
• Internal buffer: 1800 bytes.
• Power supply read: 9 - 12 V at 800 mA.
• Video output: Composite video: negative sync, 1V p-p into 75 ohms, 50 Hz frame, 15625 Hz line frequency.
• Screen format: 80 characters by 24 for lines, 64 by 16 lines for setup mode.
• Attribute: Reverse video, enabled by escape sequence.
• Keyboard: Full size, 60 key QWERTY layout, positive travel. Two shot moulded key tops.
• Microprocessor: Z80A at 3.375 MHz.
• Control program: 4k 2532 EPROM.
• Sound generation: Built in loudspeaker for BELL.
• Case: 342mm W × 239mm D × 42mm H. Injection moulded ABS.

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

Microbee 32K IC

Standard MicroBee Tapes are encoded at 300 or 1200 baud using its own variation of Processor Technology's SOLOS/CUTER Tape protocol[6] that consists of a 300 baud metadata header followed by data payload blocks encoded at the desired transfer rate using CUTS (Computer Users Tape System).[7]

The wav2dat software converts audio data into Microbee files.

A few books were written about the Microbee, including:

• Wildcards - By Robert Alan Burt, Peter Terence Ford, and Ash Nallawalla[8]
• Wildcards 2 - By Robert Alan Burt, Peter Terence Ford, and Ash Nallawalla[9]
• Wildcards 3 - By Robert Alan Burt, Peter Terence Ford, and Ash Nallawalla[10]
• Wildcards 4 - By Robert Alan Burt, Peter Terence Ford, and Ash Nallawalla[11]
• Getting started on your MicroBee - By Petr Lukes and Tim Hartnell[12]
• Shake hands with the Microbee - By Pam Kelly-Hartley, Joy McKneil and Tony Melius[13]
• The Penguin book of Microbee games - By David Johns and edited by Tim Hartnell[14]
• The Winners - compiled by the Sydney Microbee User's Group[15]

Games for the MicroBee include both original titles and clones of pre-existing games, including:

• Asteroids
• Emu Joust - a Joust clone
• Halloween Harry
• Hoards of the Deep Realm[16]
• Microspace Invaders
• Robotman - a Pac-Man clone by Paul Wilmhurst[17]
• Wumpus
• Cricket
• Toady - a word guessing game
• Lemonade Stall - a game for budding business entrepreneurs.
• Underworld of Kin - By Andy William Farrell
• Sword Quest - a dungeons and dragons style game by P Jepson and C Temple[18]
• Scrambler
• Gorilla Maths - a mental maths challenge with inklings of Donkey Kong

As well, numerous adventure games were written, mainly in BASIC, plus educational software.[19][20]

The final version of the MicroBee, released in 1987, was the 256TC. This increased the memory to 256 kB of dynamic RAM and had a new keyboard with numeric keypad. The computer had a built in 3.5" floppy disk drive supporting both 800 kB (DSDD) and 400 kB (SSDD) formats. Bundled software included "Videotex" (a videotex terminal program), "Simply Write" (a word processor) and "Telcom" (a serial terminal emulator program).

MicroBee Systems also designed a PC clone, called the "Matilda", or 640TC, which ran an NEC V40 (see NEC V20 chip), and emulated the MicroBee CP/M systems in software.

An advanced next generation model code named "Gamma", based on the Motorola 68010 and two Zilog Z80 processors, was designed but never made it to the market.[21][22]

In 1992, after having undergone a number of ownership changes, the company ceased trading.[23]

After almost 20 years, the Microbee brand was re-launched in 2012 by Microbee Technology Pty Ltd, run by a Microbee employee from the 1980s, Ewan Wordsworth.[23] The company produced a limited edition (100 unit only) kit, the Premium Plus. The new version was still Z80-based and followed the original two-board design. It had dual-processor architecture, with some enhancements such as floppy emulation of the SD memory card.[24]

Wikimedia Commons has media related to MicroBee.

• The Microbee Software Preservation Project (MSPP) - Discussion Forum, File Repository & Photo Gallery
• Discussion Forum for all things Microbee & extensive File Repository
• MicroBee Documents, Projects, Software, Advertisements, Emulators And Resources
• The PC Museum, Applied Technology page
• Matthew Geier's notes and pictures, including a working "Gamma"
• Microbee Documentation Project
• The Powerhouse Museum (Sydney Australia) - K1431 Microcomputer, "Microbee" 16KROM, early Kit computer.
• Alistair Shilton's "Archaic Electronics Labyrinth" including a page (Picomozzy - the Microbee 32k Emulator) with scans of Microbee technical reference manualsArchived version
• The Microbee ArchiveArchived version
• The Microbee story
• The Microbee Beeboard - Virtual Museum, Discussion Forum & File Repository
• Australian Computer Museum Society Inc microbee page
• OLD-COMPUTERS.COM's page dedicated to the Microbee systems

Emulators

• uBee512 MicroBee emulator
• Web-based MicroBee emulator