a 2 bit scumbag who couldn't make it in a 32 bit world.

You should be able to use both - there are 2 ROM sockets in the QL - both are wired exactly the same, so you could put the QL-SD in the right hand one as you look at the front, and the rom switcher in the left socket.

And there was I thinking it was a new regional metric measurement !

looks like those 4 simms are soldered - but for 256Kb they must be 64Kb in size !!

This is pretty much the circuit used in the OPD: http://www.openmusiclabs.com/learning/digital/input-scanning-matrix/dual-shift-mux/index.html There are 2 extra lines on the 20 pin ribbon from the keyboard, that I think carry keypress details for specific functions keys on the keyboard (resume, etc)...

vanpeebles wrote:I take it those two registers are not very good?

oops - I love a good typo in the morning....

I remember a highly addictive game called Kye on the PC - a puzzle game with many levels - the last ones quite devious.

Boxworld was another fun but pointless game too

bookmarked for later perusal - some interesting articles and toolkits for sure

I must confess it's the hardware for me - but I do appreciate that the hardware would be nothing without good software support.

I forgot to add in my diagnosing that the keyboard for the OPD is handled by 2 shit registers, and the clock, clear, shift data in and out and the parallel load are all signals routed to the off board modem / telco unit. This has an on board 8051 chip which appears to be handling the reading of the ...

Attached is a PDF with some further info gained by some reverse engineering on the boards I have.