6809 SBC

Ther 'tube' was an interface on the BBC micro ro link up a so-called second processor. The connector on the Beeb carried a subset of the system bus signals (8 data lines, a few address lines, an address decoder output, r/w, and so on). THe second processors, at least the official Acorn ones, had a ULA chip that contained a couple of FIFOs to act as an interface between the 2 machines. The reason for the name of that article is thus obvious. THe Dragon was, of course, the most common 6809-based computer in the UK. The name 'tube' came from the fact it was a connnection to trasnfer data between the 2 porcessors, also becasue the London Underground (railway) is commonly called the Tube. In that sense it is an alternative to a bus (as a form of public transport), I am sure the connection between bus and tube was appreciated at Acron. The Tatung Einstein's system bus was called the 'Pipe', presumably as a pun on 'tube'. Were they? I've never heard of one. Acorn never (AFAIK) made a 6809 second processor for the BBC micro. The original series of second processors (in 'chesse wedge' cases to fit alongside the BBC micro) were the 65C02, Z80A, 32016 (originally 16032 :-)) and ARM 1. There was also a 32016 board with 4 times as much RAM that was used in the Acorn Cambridge WOrkstation There were internal second processor boards for the Master series, including a 80186-based one. But I've never heard of a 6809 one there either. Is this article available on-line anywhere? Or do you have a reference to it? It sounds as though it might be worth reading. -tony