Manuel Polik wrote:
> BTW: In QB, there's this sethorpos routine, written by Andrew and
> improved with suggestions from you. I've just found yet another
> improvement!
> Looky here!
>
> This is the end of the routine in QB:
>
> ----------------------------------------
> sta HMP0,x
> sta WSYNC
> jsr Ret ; Waste 12 cycles, 3 Byte
> bit 0 ; Waste 3 cycles, 2 Byte
> ; + sum: 15 cycles, 5 Byte
> Jiggle dey
> bpl Jiggle
> sta RESP0,x
> ----------------------------------------
>
> Here's my idea:
> ----------------------------------------
> STA HMP0,x
> INY ; Waste 5 cycles, 1 Byte
> STA WSYNC
> INY ; Waste 7(!) cycles, 1 Byte
> BIT 0 ; Waste 3 cycles, 2 Byte
> ; + sum: 15 cycles, _4_ Byte!!!
> PosDelay dey
> bpl PosDelay
> STA RESP0,x
> ----------------------------------------
>
> Apart from saving a byte, it prevents you from possibly losing another
> two byte to the stack...
> (Avoiding that was my original intention, in Gunfight there's _never_ a
> subroutine call within a subroutine call within a subroutine :-))
Yes, that should work, but sometimes you might waste a hole scanline when your first additional dey causes WSYNC to start to late.
You might have a look at this:
----------------------------------------
sta HMP0,x
sta WSYNC
iny ; waste 7 cylces, 1 byte
iny ; waste 7 cylces, 1 byte
Jiggle dey
bpl Jiggle
sta.w RESP0,x ; waste 1 cylce, 1 byte
; sum = 15 cylces, 3 bytes
----------------------------------------
One more byte saved and the WSYNC problem is gone too :)
Have fun!
Thomas
_______________________________________________________
Thomas Jentzsch | *** Every bit is sacred ! ***
tjentzsch at web dot de |
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