General followup

[Theo Markettos]

I've just been reading the mailing list archives, and I've got a couple of
responses that might be useful...

If you want a 16 bit sound circuit, you could have a look at my Risc PC
16-bit sound upgrade at http://www.markettos.org.uk/riscos/16bitsound/ - I
think the 7500FE sound output is basically the same.  I'll try my upgrade
on my Bush box when it arrives to see whether it works.

As for floppy-over-parallel, does the Bush box have ADFS resident?  The
37C66x supports this mode - I've almost got it working under RISC OS, but
it needs the INDEX line to be connected to the floppy interrupt to work
(and I didn't feel like hacking my Risc PC to do this).  If ADFS is
resident (do *Help ADFS) then fitting a floppy drive should be fairly
trivial.  If not, it should be possible to softload it as long as the
floppy interrupt to the 7500 is accessible.  If you can get ADFS and DOSFS
onto the box, it should be possible to read DOS floppies.

I'm told by a Pace person that the bodge resistor is to fix a bug on the
podule bus.  When RISC OS boots, it scans the podule bus to see if it can
find any 'Acorn conformant expansion cards', indicated by bit 7 of their
first word, and if so tries to read their identifier ROM.  The problem
being that on the Bush box, nothing lives at this location, so you just
get random data returned.  If this random data happens to look like a
valid podule, RISC OS will try to load it, resulting in all sorts of
horrid crashes.  I'm told that the ROM images had already been shipped off
for manufacture in Turkey when this was discovered - hence the inclusion
of the bodge resistor, which forces the podule bus to look as if all
podules are invalid, and hence ignored by RISC OS.  I think the modem
driver is then hard-coded to expect where the modem chipset is, without
the usual podule finding mechanism.

I'll see if I can have a play with my box to test these when it arrives...

Theo

-- 
Theo Markettos                 theo@markettos.org.uk
Gonville and Caius College     theom@chiark.greenend.org.uk
Cambridge, CB2 1TA, UK         http://www.markettos.org.uk/