Acorn meetup at the weekend (March 2022)

ABUG used to meet a couple of times a year and at the weekend resumed, at reduced capacity for safety reasons. It’s Acorn-centric, both 8 bit and 32 bit, so we saw Electrons, Beebs, Masters, as well as the odd Atom, and also Archimedes and RISC PCs. But there was also a rebuild of a super-rare dual-6809 prototype from Dragon (just before they collapsed) and for myself and @Revaldinho we mostly worked on the Pi-in-CPC gadget which we first displayed at the same event a couple of years ago…

You’ll see in that album some dim photos and a QIX-like video demo of what we got working this time: some machinecode extensions to Basic allow VDU output to be piped through the FIFO board to the Pi, which is running a BBC Basic on Linux and displaying fullscreen on HDMI.

So, it’s a bigger faster more colourful graphics output for the CPC - but in principle for any computer that can accept an 8 bit peripheral. At least one person is interested in adding it to an Archimedes.

As we have a bidirectional bytewide channel with flow control, there’s no constraint on the performance of the Pi end, and we can use C, Basic, or Python - all of which have been benchmarked - or of course machine code.

Our next step will be to upgrade the protocol to multiplex various purposes - if a Pi can do it, we want access from the CPC. So, that would include sound, mass storage, real time clock, network access - as well as graphics output.

Oh, here’s the demo:

See this thread for the Basic.

I did run a little bit of code on my Beebs too, of course! In particular I was able to demo the HDMI output from PiTubeDirect, which gives a massively fast and high resolution VDU output from the Pi’s HDMI, for code running on the Pi (as a second processor - 6502 code, z80 code, x86 code, 32016 code, ARM code…) and possibly with a bit of footwork could also provide VDU output for code running on the host Beeb.

@Revaldinho was pleased to see that his Beeb816 add-in was still working, after being unused for a bit. That gives us a real 65816 in the Beeb (or Master, or Electron) with lots of fast RAM, and there’s even an 816-mode BBC Basic port which offers some 180k of memory space.

There was also a lot of socialising and chat, which is good and as expected. (There was, as it happens, rather little by way of mask-wearing, so we will see if we got away with it.)

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