On Mar 12, 10:08, Mike wrote: Externally, practically nothing. Internally, the Sorcerer II has somewhat different memory decoding, to accomodate 3 rows of 4116's instead of 2, and they're all socketed. There's a DIP switch to select type and number of banks, which was done by solder links on the original. The video timing is also different, and it's easier to get a stable picture at 50Hz on the Mk.II; one of the poles on the 4-way DIP switch controls US/UK setting. Some of the signals on the 50-way expansion interface are slightly different. There's an MEMORY OFF input so an external device can switch off the internal RAM. The RSET signal is derived slightly differently, too. The Mk.II has fixed the hardware bug in the RS232 (on the Mk.1, the gate signal to switch from cassette to RS232 was wrongly applied so the RS232 was forced to the wrong logic level when the cassette was selected). Some of the layout is a little different to accomadate the changes, the IC number has changed of course, and a few parts of the circuit are done with (parts of) different ICs. They're still the same clock speed (2.106 MHz), and (apart from the differences above) the same machine. -- Pete Peter Turnbull Network Manager Dept. of Computer Science University of York