30 Aug
2006
30 Aug
'06
6:09 p.m.
"Henk Gooijen" wrote:
The only difference between CLR and MOV #0 that I think of immediately
is that CLR clears the Carry flag too, whereas MOV #0 does not affect the
Carry flag.
That is functionally correct, but I don't believe the two are
implemented that same (in microcode or hardware) in terms of what they
do on the UNIBUS.
My question was more, "in the various pdp-11 implementations", does CLR
generate a read-modify-write (DATIP,DATO) on all the machines?
A read-modify-write cycle on the unibus is not the same a normal read or
write. I thought I could just ignore it but it turns out I can't (but
it's not hard to support).
-brad