Hi Si, Yep - clear as mud! :-)
Seriously, many thanks for the explanation - even my hardware-limited brain managed to understand all that! I take my hat off to hardware designers, it's certainly a black art! I've always tried to keep as much as I can in registers, so I've always been on the right tracks - even if I'm always pretty close to derailing! As for IX and IY - useful though they are - they've always been dogs even using official Z80 timings. So I've always tried to avoid using them in anything remotely time-critical. A potential 48Ts... Ouch! As for using SimCoupe's built in debugger - I certainly do! It's a very useful feature. :-) Thanks again, Chris...
