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Forums > C64 Coding > D017 stretch
2017-01-31 09:47

Registered: Jan 2002
Posts: 103
D017 stretch

I have a little while trying out som d017-stretching-code-magic-stuff. It seems impossible to stretch sprite 00 when it is alone a raster row.
Can anyone confirm it is possible or tell med where I am going wrong? I just cant get the timings right and I've tried all combinations (I think?).

I've put 1 -> d017 on all cycles after dec $d016 and then 0 on all cycles after that but for me it seems impossible...

Any help at all would be greatly appriciated!

lda #1
ldy #8
-		dec $d016		;  6 Removes the border
		cmp #$c9
		sta $d017		; Has been moved around
		cmp #$c9
		bit $ea
		sty $d017		; Has been moved around
		cmp #$c9
		cmp #$c9
		cmp #$c9
		cmp #$c9
		cmp #$c9
		cmp #$c9
		cmp #$c9
		cmp #$c9
		cmp #$c9
		cmp #$c9
		cmp #$c9
		cmp #$c9
		cmp #$c9
		cmp #$c9
		sty $d016		; Makes sure the border is removable
		cpx #15
		bne -
... 11 posts hidden. Click here to view all posts....
2017-01-31 19:44

Registered: Dec 2001
Posts: 8517
never put your thumb into the sideborder, girlfriend said
2017-01-31 22:38

Registered: Feb 2003
Posts: 281
let's make a demo about it.
2017-02-01 00:09

Registered: Jan 2002
Posts: 103
Sorry for my stupid question, of course it works to stretch a single sprite with d017 while removing the border (even S#00). You just have to stop being stupid and do it the right way :-(
2017-02-01 00:49
The Phantom

Registered: Jan 2004
Posts: 353
Meh. Whatever.

Good luck.
2017-02-01 07:42

Registered: Apr 2002
Posts: 4233
NOS intro at DOTC 1 sided is having sideborder off + 8 sprites stretched differently ?

Defender of the Crown +9D
2017-02-01 08:32

Registered: Feb 2003
Posts: 670
..isn't that what i told you from the beginning Trash? Just do it the right way! :)
2017-02-01 08:44

Registered: Jan 2002
Posts: 103
Quote: ..isn't that what i told you from the beginning Trash? Just do it the right way! :)

According to you everything is easy, just some lda and sta's in the right place and the sky is the limit...
2017-02-01 10:05

Registered: Jan 2005
Posts: 330
For some reason when doing an 8-sprite open border routine you have to use DEC $d016 + INC $d016.

This has something to do with sprite 0 DMA eating too many cycles from the CPU, so the $d016 writes don't happen at the right time, occupying the CPU with DEC/INC solves that.

I found this out the hard way, back when I still actively coded demos. The explanation might be a bit off, but I'm sure there's VIC-II guru's out here who can do a better job than I do.

But like others have mentioned, when you don't need all 8 sprites, avoid sprite 0.
2017-02-01 10:41
Account closed

Registered: Dec 2002
Posts: 990
Explanation is easy: DEC $D016 has 2 write cycles at the end of it's execution, while STA $D016 has only one. The 6510 cannot be stopped on write cycles, so with the right timing you can skip 2 of the 3 bus allocate cycles of the sprite #0 DMA which gets you right to the exact cycle where $D016 has to be changed to open the side border.
2017-02-01 11:42

Registered: Jan 2005
Posts: 330
Thanks Graham,

That explains the sprite 0 nastiness a lot better than I did :)
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