Date   : Tue, 28 Jan 2014 03:27:49 +0000
From   : jgh@... (J.G.Harston)
Subject: Torch Graduate

Jules Richardson wrote:
> I seem to recall that it hooks up via the 1MHz bus rather than the Tube;
> I'm not sure what firmware is needed on the beeb side (I assume the beeb
> can be used to make it "do stuff" rather than it purely being the other way
> around, with the beeb just acting as keyboard and display)

There's a clever trick where a 1MHz peripheral can take control of the 
Beeb without there being any code in the Beeb.

On RESET, after doing most of the startup setup, before looking for any 
ROMs, the MOS briefly enables interrupts. If an interupt was pending 
because IRQ has been held low since RESET, then a call is made to 
(&FDFE).

So, what you can do is page code into FRED and/or JIM, with &FDFE 
pointing to your code in FRED/JIM, tie IRQ to RESET, and have your code 
that pages into FRED/JIM page through external memory and copy itself 
out into main RAM, cling to any vectors, and take control of the machine 
- or give it back for RESET to continue. Essentially, the same procedure 
as used with RISC OS podule code.

-- 
J.G.Harston - jgh@...      - mdfs.net