BBC Micro - Z80 Second Processor Upgrade

The Tube Interface

The Tube is an expansion interface built into the BBC Micro which was designed to enable the computer to communicate with a second processor. The BBC Micro host processor would then handle the Inputs and Outputs (I/O) while the second processor took over program execution. Available Second Processors included a higher speed MOS 6502 running at 3MHz, a Z80 running at 6MHz, a NS32016 running at 6MHz as well as an ARM Evaluation System using an ARM1 processor running at 8MHz.

The Second Processors, and other options like the Teletext Adapter and Prestel Adapter, were all built into wedge shaped enclosures, often called "cheese wedges", which sat side-by-side with the BBC Micro as shown in the photo of the Teletext adapter above, connected via a ribbon cable to the Micro's Tube interface port. The photo on the right is a Z80 Second Processor, the picture was downloaded from Chris's Acorns.

Z80 Second Processor

The Z80 Second Processor was supplied with a copy of CP/M 2.2 and a number of bundled programs :-

To use the Z80 Processor upgrade, the BBC Micro required a disk interface and a pair of 80 Track disk drives. Although the Beeb continued to drive the TV output, the display of 80 column text really required the use of a colour or monochrome monitor.