PiTubeDirect

The first commercially available Acorn RISC processor was released as a co-processor for the BBC Micro. Acorn always had processors on the mind it seems as the Tube interface and protocol [1] is solely for co-processors. There's an excellent Rasperry Pi based project, PiTubeDirect, which emulates the ARM and many other co-processors on original Acorn 6502 based hardware; Atom, Electron, Micro and Master [2]. The original expansion hardware is, as expected, incredibly rare and valuable. [1] https://mdfs.net/Info/Comp/Acorn/AppNotes/004.pdf [2] https://github.com/hoglet67/PiTubeDirect

The most interesting things here are disk images for the Master "512", which despite the name was a fairly normal Master 128 only with the addition of an Intel 80186 co-processor, carrying 512k of RAM on its own board. It could boot "DOS Plus", a DOS clone from Digital Research that included the GEM desktop. Unfortunately it was compatible with very little DOS software, being system call compatible only up to MS-DOS 2.1, and having a non-standard keyboard and display. As far as I know Acorn only shifted any significant amount of stock after they slashed the price, and I wonder even then how many buyers thought they were getting a BBC Master with 512k of RAM. I suspect most of the copro cards went unused. Today, if you have a Master 128 and want to "upgrade" it, you can run PiTubeDirect on a Raspberry Pi which will cause it to emulate the

See also, PiTubeDirect[1], which runs on a Raspberry Pi which you have plugged into the second processor port of a BBC Micro[2], and turns the Pi into emulator for a number of different processors, notably an arbitrarily fast 6502, a Z80, or an 80286. [1]: https://github.com/hoglet67/PiTubeDirect [2]: https://en.wikipedia.org/wiki/BBC_Micro_expansion_unit#Secon...

IMHO this makes the PiTube Direct project perhaps even more impressive: it attaches emulated vintage microprocessors to the BBC Micro Tube interface, implementing the Tube circuitry in software. https://github.com/hoglet67/PiTubeDirect

There's a similar project for the Acorn BBC Micro called PiTubeDirect, which allows the Pi to emulate several different CPUs, while connected to the BBC Micro's "tube" second processor slot. https://github.com/hoglet67/PiTubeDirect (The BBC Micro itself was quite remarkable for supporting multiple processors, which did not have to be the same architecture as the host 6502. Amazing for 1981.)

See PiTubeDirect: https://github.com/hoglet67/PiTubeDirect/wiki https://magpi.raspberrypi.org/articles/pitubedirect

BBC Micro can run Doom too https://www.youtube.com/watch?v=V6HQrXCRZsw Just add a Tube co processor and replace the graphics hardware https://github.com/hoglet67/PiTubeDirect/wiki https://stardot.org.uk/forums/viewtopic.php?t=13632

Yes it really was well thought out. Another good example is the 'tube' interface for second processors. Enthusiasts have recently put this to use to interface with a Raspberry Pi which can emulate various processors from back in the day at unheard-of speeds, and also provides a modern native ARM coprocessor. The neat thing is that this all works with no changes to the BBC and no special software; you just use the operating system routines as usual on code running on the second processor and it all just works. Not bad for a system designed in 1981. https://github.com/hoglet67/PiTubeDirect/wiki

The project's wiki might actually be a better link: https://github.com/hoglet67/PiTubeDirect/wiki