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