For background, in case anyone doesn't know (huh, I was just discussing this here last week)... The BBC Micro Tube interface is a fast interface which allows a

For background, in case anyone doesn't know (huh, I was just discussing this here last week)... The BBC Micro Tube interface is a fast interface which allows a second, quite different computer to use the BBC Micro as an I/O processor. Acorn made several: the most popular was a 3MHz 6502, but there was also a Z80 model which ran CP/M, a NS32016 with 1MB RAM which ran a custom OS, the famous ARM1, etc. The second processor communicates with the BBC Micro via RPC, and can make any system call. The BBC Micro provides graphics, filesystems (including hierarchical disk and network filesystems), printer, keyboard, etc, all in a completely portable fashion. (The BBC Micro operating system was really rather good.) This keeps load on the second processor down. No I/O interrupts, no need for drivers, no real need for an OS if you don't want one; the 6502 second processor had a 2kB ROM and everything else in the address space was user RAM. It looks like what this is doing is bit-banging the BBC Micro Tube interface and emulating a 6502 in software, so it's pretending to be a classic 6502 second processor (rather faster than the original!). Here's a different project: http://www.stardot.org.uk/forums/viewtopic.php?f=44&t=8852 http://www.stardot.org.uk/forums/viewtopic.php?f=44&t=8852 It's an FPGA-based second processor module which (if I read it correctly) can be programmed with a soft core to be a 6502, 68000, 6809, Z80, 32016 or PDP11 second processor. Some crazy person seems to have even ported BBC Basic to the PDP11...