Acorn Second Processors (was: Re: Quick survey on equipment)

On 26/04/07, Ensor <classiccmp at memory-alpha.org.uk> wrote: [on Z80 add-on processors] > I suppose I could always make one, assuming the necessary ROM images are > available somewhere? I don't recall there being any custom logic in the 6502 > Second Processor and my memory of the Torch Z80 2nd processor is waaay to > hazy. Acorn used a custom "ULA" chip to handle communications between the second processor, of whatever flavour, and the host BBC computer. This provided a handfull of FIFOs and signal lines in both directions. Torch used a pair of PIO chips connected back-to-back to provide simular but incompatible functionality; only their ROM software could understand it. The Acorn one has definiatly been emulated, in Sprow's AEM7TDMI co-processor for example: <http://www.sprow.co.uk/bbc/armcopro.htm > Which brings me onto a second point. I actually have at least one BBC > "Master" too, I have a vague recollection that these have a connector for an > internal, as well as an external, second processor? They do. You can connect up to both, and *CONFIGURE the system to use which ever one you want (or neither, but not both.) > Do you know of any websites where I could get more info? Sprow's page above has a link to Acorn's Tube application notes - that should get you started on how the tube actually /worked/ .. Whilst not wishing to remove an 8-bit thread from cc, you are probably best asking for technical info over on the bbc micro mailing list - gioto <http://lists.cloud9.co.uk/mailman/listinfo/bbc-micro> for subscription machine. Rob