Geoff Winkless wrote:
> OK, so my memory isn't too hot. Given that this code will
> probably execute in screen time, is it quicker to do:
Ok, my first post here in ages, here goes...
Simplistic rule of thumb for timings on SAM - an instruction's cycles is
the official Z80 cycles rounded up to the next multiple of 4 (or 8 in
screen time), or, 4 (or 8) times the number of memory accesses;
whichever is greater. When INs and OUTs are involved things get more
complicated!
E.g. (official/SAM normal/SAM screen)
INC A - 4/4/8
INC HL - 6/8/8
So -
LD A, (HL) - (2 memory accesses) - 8/16
AND C - (1 memory access) - 4/8
LD (HL), A - - 8/16
= 20/40
Or -
RES 0, (HL) - (4 memory accesses) - 16/32
RES 4, (HL) - - 16/32
= 32/64
> It seems that method 2 runs quicker. I'd like to know why :)
Mmm, I'd have thought the first method would run quicker, even when it
was AND &EE. I'm confused now. Anything else going on in the loop?
Hi all,
Dave.
