Sorry, but i do get rather confused with this thing from time to time :o) I'm getting a "R/W Error @ F800 BTS 08" when trying to test the ram on one of these MCR boards. Am i right in saying that i need to be tracking down a problem on the data bus, bit 4, bit 3 if you prefer your numbers to be 0 based (1000 = 8, therefore, that's bit 0, 1, 2, then 3 or 1, 2, 3, then 4). And if it were a decode error then that would be the address bus? I'm assuming all is well with chip selects and r/w signals since it's only complaining about bit 08 and not FF? As an aside, i burnt a set of home burnt roms but the 9010 still can't read the things reliably in the MCR sets. It doesn't seem to like anything that's in close relation to the CTC i don't think. It's happy enough troubleshooting the video staging ram and the background ram, just not the program ram or rom :( I'm using a normal Z80 pod with a Z80A processor in it. I'm guessing from reading previous posts that there would be no benefit in trying to blag or borrow a Z80AA since someone else was saying that couldn't cope with MCR hardware either. Martin. _______________________________________________ Techtoolslist mailing list Techtoolslist@flippers.com http://seven.pairlist.net/mailman/listinfo/techtoolslist