From: utzoo!decvax!ittvax!sii!mem Newsgroups: net.micro.68k Title: Re: Warning: Don"t use the "clr" instruction on device registers Article-I.D.: sii.265 Posted: Fri Mar 11 00:52:44 1983 Received: Sat Mar 12 00:55:59 1983 References: pyuxmm.401 c Re: not using the CLR instruction on device registers. True. Also don't use the CLR instruction, or Scc, on memory which has parity checking because of the read-before-write problem. Relatedly, you'll notice that the manual says that MOVEM (move multiple) does an extra bus cycle. This ALSO loses if you're pushing registers into uninitialized memory which has parity (or other error) checking. Mark Mallett