
PiTubeDirect: A Raspberry Pi as a BBC Micro Second Processor - fanf2
https://github.com/hoglet67/PiTubeDirect/wiki
======
myelin
For more background on the whole Second Processor system, see the "Acorn's
Second Processors and the Tube - what, and why" thread at Stardot:
[http://www.stardot.org.uk/forums/viewtopic.php?f=3&t=14211](http://www.stardot.org.uk/forums/viewtopic.php?f=3&t=14211)

On that note, Stardot is a small but thriving community around the BBC Micro,
and Acorn Computers' other machines -- the Acorn Atom, Acorn Electron, BBC
Master, BBC Master Compact, and the Archimedes/RISC PC machines. The author of
PiTubeDirect is an active poster there, and the tone is generally very
friendly and on-topic. I've been reading/posting for the last year or so and
it's turned Acorn-focussed retro hardware into my favourite hobby. I'd highly
recommend taking a look if you used/loved one of these machines back in the
80s/90s.

~~~
leggomylibro
Wait...Acorn as in 'Acorn RISC Machine'/ARM? I didn't know they made actual
consumer hardware, that's pretty cool. Sort of funny that the modern BBC
Micro:bit went on to run on a Cortex-M0 core.

I also kind of love that the BBC's learning hardware calls its method of
routing instructions to coprocessors 'The Tube'.

~~~
cjsuk
The early ARM machines didn’t really make it out of the U.K. I had some early
Acorn/ARM stuff in 1988. It was by far the most advanced bit of kit at the
time. Literally smoked everything and did so for a number of years afterwards.

Example: 1987 graphics demo:
[https://youtu.be/653Ger80ros](https://youtu.be/653Ger80ros)

They even did a line of unix workstations!

Nice video on the matter here from 1987: [https://youtu.be/hrj-
EEnsacQ](https://youtu.be/hrj-EEnsacQ)

~~~
Fnoord
Acorn Archimedes - A Technical Introduction - 1987 BBC VHS Video. [1] Quoting
from YouTube description: "Fred Harris talks to Roger Wilson about the
technical aspects of the Acorn Archimedes A305. Also features footage from
Zarch by David Braben. Produced by the BBC. Digitised from VHS Video Tape by
The Centre for Computing History."

According to Wikipedia [2]: "The Acorn Archimedes was the first RISC-based
home computer." and "The Archimedes was one of the most powerful home
computers available during the late 1980s and early 1990s". Article also
includes basic performance comparisons with m68k (Amiga & Atari).

[1]
[https://www.youtube.com/watch?v=KKTa54UikgE](https://www.youtube.com/watch?v=KKTa54UikgE)

[2]
[https://en.wikipedia.org/wiki/Acorn_Archimedes](https://en.wikipedia.org/wiki/Acorn_Archimedes)

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bri3d
Driving the databus GPIO pins using the VideoCore as a second processor is a
really clever hack, especially on the single-core Pi Zero. I guess it's
logical that the GPIO can be driven by the GPU in this architecture but I
never really thought to do it before.

~~~
onesun
Came to say this. I wonder if this hack is widely known, because it seems like
this is a pretty clever way to use the Pi Zero in some applications that would
be better served with a multi-core processor and don't require the GPU for
video tasks. Hacking the Pi Zero to be a dual-core system essentially.

~~~
b3lvedere
Could four Pi Zeroes become a Pi 3? :)

~~~
shakna
Clustering the Pi has always been fairly easy [0].

[0]
[http://www.southampton.ac.uk/~sjc/raspberrypi/](http://www.southampton.ac.uk/~sjc/raspberrypi/)

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jacquesm
Hah, neat to see the 32016 mentioned, I still have a pre-production series
sample of that chip somewhere in storage.

Super cool this, I'm _almost_ tempted to score a Master or a Model-B on ebay
or mp to replicate this but there just isn't time enough in the day to get
sucked into retro computing. Extra points if they ever manage to port the
basic to the native Pi including inline assembly, that would be a pretty neat
environment to develop stuff for the Pi in.

~~~
pmyteh
There is a native port to the Pi of RISC OS, the ARM-based operating system
that ran on Acorn's successor to the BBC (the Acorn Archimedes). The BASIC on
that is also BBC Basic, including inline ARM assembler.

[https://www.riscosopen.org/content/downloads/raspberry-
pi](https://www.riscosopen.org/content/downloads/raspberry-pi)

~~~
watmough
BBC Basic for x86 systems also includes the inline assembler.

[http://www.bbcbasic.co.uk/bbcbasic.html](http://www.bbcbasic.co.uk/bbcbasic.html)

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cjsuk
Now that’s what I come here for. I had a Master with 65C102 coprocessor
(internal one) and I still claim to this day that it was the finest machine I
have ever used. Rather cool what you can achieve with the tube even to this
day.

~~~
gaius
You’re not wrong. Mine is setup on my desk at home and still gets regularly
used.

~~~
cjsuk
Glad to hear it. I’m scouting for one on eBay now :)

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digi_owl
For some reason i thought this involved the Micro:Bit.

[https://en.wikipedia.org/wiki/Micro_Bit](https://en.wikipedia.org/wiki/Micro_Bit)

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toyg
To really close the circle, someone should implement this hack with a BBC
Micro:bit, which is the spiritual successor to the original Micro.

------
salgernon
Are BBC Micros or other Acorn machines generally available outside of the UK?
I don't recall having seen one on eBay in the US (at least, not when I went
looking..) I would imagine 80s systems were designed to use PAL rather than
digital output?

~~~
myelin
I've seen a few from US-based sellers on eBay, but most are in the UK. Pretty
much everyone I've met in the USA with Acorn hardware grew up in the UK and
moved here.

I use an RGB-to-HDMI converter (this one --
[https://retrocomputing.stackexchange.com/questions/2553/acor...](https://retrocomputing.stackexchange.com/questions/2553/acorn-
electron-to-vga-hdmi/2968#2968) ) and connect my BBC and Electron up to a
normal HDMI monitor. The native video format is 1-bit RGB with TTL levels,
with a 50Hz refresh rate (possibly interlaced -- I forget).

