[stella] NOT skipdraw

Subject: [stella] NOT skipdraw
From: "Thomas Jentzsch" <tjentzsch@xxxxxx>
Date: Tue, 22 Feb 2005 06:29:36 -0500
Hi,
while we are waiting the list to be moved to a new home, I
though it might be a good idea to do some coding in between.

Here is some skipdraw replacement code, which works
even faster than the original routine (18 cycles for constant
heights, 19 for variable heights):

  cpy   switch  ; 3
  beq   .switch ; 23
  bcs   .wait   ; 23
  lda   (ptr),y ; 5
  sta   GRPx    ; 3
.cont:          ;   = 15
  ...

  ...
.switch:        ; 6
  lda   end     ; 3
  sta   switch  ; 3
  bcs   .cont   ; 3

.wait:          ; 8
  SLEEP 4       ; 4
  bpl   .wait   ; 3

While it is faster, it has some disadvantages. But I thought it
might become useful for someone, sometime, somewhere... :-)

BTW: I had used a similar code in Thrust and just recently
"rediscovered" it. :-)

Have fun!
Thomas
_______________________________________________________
Thomas Jentzsch         | *** Every bit is sacred ! ***
tjentzsch at web dot de |



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