On Friday 05 January 2001  7:19 pm, Ignatios Souvatzis wrote:
> On Fri, Jan 05, 2001 at 07:03:17PM +0000, Ben Harris wrote:
> > >I can't remember offhand how to reach these IDs, but Acorn called them
> > >Unique Machine IDs.
> >
> > They're in a Dallas Silicon Serial Number chip (erm DS1401?) attached to
> > one of the control pins on the IOC/IOMD.  Access (as with the I^2C bus on
> > these machines) is by bit-banging over the control register.  Currently,
> > neither port has code to do this (arm32 gets the ID from the bootloader).
>
> Oh... thats, maybe the same chip, or at least the same access method, as
> what the DraCo uses! It's a DS2404 there, which includes a battery backed
> clock.

The Risc PC one is a 3 legged thing, bit like a big transistor, I think it's 
a DS2401.  (Note I assume this as it's one of the 3 chips on the board that 
is socketed (the other 2 being for Risc-OS))

Anyway the text on it is:
DS2401
9532B1
MALAY
439AU

It goes in IC17, to the SE of the IOMD in a Risc PC.

Cheers,
Chris