Hi, I just did a bit of "Googling"; seems the Memotechs could run CP/M when fitted with the "FDX" expansion "chassis". I never did manage to track one of those units down. They were pretty nifty gizmos which could house 2 floppy drives, a hard drive and Memotech's own "Silicon Discs" (aka ramdiscs) amongst other things. They also came with an internal 80 column video card to make CP/M usable. :-) The really odd thing is that I can find no mention whatsoever of the "SDX" disc unit which I had...? The SDX was a very simple unit, consisting of a single half height FD in a case with PSU and the interface which took the form of a "cartridge" which was the same shape as the computer and plugged in on the right hand side of the machine (you had to have a couple of internal expansion cards fitted to extend the expansion bus out to the edge of the case). This was most definitely a genuine Memotech product, but information on it was thin on the ground even "back in the day". Hmm, same problem as the Model III then (ISTR that had its ROM located at $0000 too, hence the reason for the Model IV). Ouch....I can see that being somewhat "problematical". ;-) Hmm, sounds like these are probably going to be as easy to get hold of now as hen's teeth...? Think I'll just get a Z80 Second Processor for my Beeb instead (far less hassle). TTFN - Pete.