Excalibur 64

 Back in the day, early 80's, there were many Australian companies vying for a piece of the emerging home computer market. Microbee is probably the most prolific. It managed to get their computers into many schools. But there are many that experienced varying degrees of success. The Excalibur 64 was not one of them. Full story below but it had a short history but not many were made. 

In the tradition of dragging late 20th century computers into the 21st this project hopes to recreate one using a mixture of old and new parts. Idea is to use modern components when it doesn't effect the function or IO. For example instead of using two 2764 EPROM just use one monster 1Mb 39SF010 flash IC. But then using the original 8253 timer IC for the audio and the MC6845 for the video.

No substituting with microcontrollers or FPGAs all the obsolete parts are available as new old stock so no excuses. But might use a RPi Pico for video or EPROM emulation for development but not for the final product.

If I could ever get hold of a PCB layout I would like to make an exact replica until then it will be just redoing the pdf version into Kicad and hope the orginals are accurate and I don't make too many mistakes. Already on version 3 of the PCB

Info at a glance

Name  Excalibur 64
Manufacturer  BGR Computers P/L
Introduced 1st July 1983 
Discontinued  31st August 1984
Cost  $399

Processor  Zilog Z80 CPU Clock  4Mhz

Microsoft BASIC built in, CP/M compatible
Memory 

DRAM 64k

ROM   16k

Screen RAM 2K SRAM (separate from user RAM)

Connection 

2 expansion connectors

Cassette I/O

Video RF Output and RGB

RS232C

Centronics Parallel Port

2 Floppy drive connectors via expansion card

Video

16 foreground and 8 background colours

Display: 24 lines by 40 characters and 24 lines by 80 characters, 7 x 12 dot matrix.

Resolution: Low res 320 x 288, 

Graphics Mode: 128 programmable characters, 96 ASCII characters and 128 graphic characters.

Peripherals

A range of peripherals, or add-ons' were developed for the machine by Mick Gulovsen and these included 

1. A RAM upgrade from 64k to 512k
2. 1200/75 baud internal modem used to connect to [[FidoNet]]
3. Keyboard buffer that could buffer up to 16 characters
4.  HIRES graphic add-on board increased the resolution to 640 x 288 pixels
5. Other peripherals had been developed by various users. 

Complete Systems

Later versions were sold as a complete system and included:

1. Dual 5 ¼ inch floppy disk drives 
2. CP/M 2.2 Operating system and later CP/M/ZCPR 3.0 and 3.1 
3. Programming languages Forth, Pascal, and Fortran on ROM and Tape
4. Increased CPU speed from 3.5Mhz to 4Mhz
5. Joystick controller
6. Voice synthesiser

History

The Excalibur 64 was a kit computer released by the now defunct Australian company BGR Computers. The Excalibur 64 sold from July 1983 to August 1984.

BGR Computers was established January 1983 with the intent of developing a system similar to the MicroBee to a foot hold in both the educational and business markets. The company at time wanted to develop a complete system but the costs of development and availability of software made this prohibitive.  Therefore, to enter the fledging home computer market BGR engaged an independent design company to develop a diskless kit which was first advertised in the July's 1983 edition of Electronics Australia .

More that 300 kits were sold and with the help of user groups the software catalogue grew and included, games, utilities and educational programs. 

By December 1983 the Excalibur 64 was released as a complete system the retail price jumped from $399 to $699 but was fully built and tested. This price did not include a monitor and a disc controller board that could run up to four 5 ¼ or 8-inch drives would cost a further $299. 

Reception

It is believed that just over 1000 units were sold. User groups were established across the country and were active 

Useful Links

Dontronics Excalibur

Some Images

Floppy Drive controller 5.25" and 8"