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Testa
Account closed
Registered: Oct 2004
Posts: 197 |
lucky timing. stable rasterirq without stablelize routine
hi,
i was looking through some old code of my and i found an old demopart witch has open sideborders, music, and i didn't use any stablelize routine... it is 16 years ago and i still don't know how this works...
the demo that i am talking about is explicit and the part is called... noteparty.. it starts at hex 4000 ...
the part is terrible but the logo is nice... anyway,
it uses a normal interupt setup and the irq vector is directly pointed to the sideborder rastercode.. no problem at all...
how is this possible...
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chatGPZ
Registered: Dec 2001
Posts: 11386 |
automagic stableness by doing read/modify/write instructions on a rasterline with 4 sprites ? :) |
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Testa
Account closed
Registered: Oct 2004
Posts: 197 |
well. i honestly don't know how it works and how save it is... but it is stable on a real c64 and in vice...
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Devia
Registered: Oct 2004
Posts: 401 |
sprites are automatic stabilizers if used correctly.. check out Sprite synchronisation for some related info.
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SIDWAVE
Account closed
Registered: Apr 2002
Posts: 2238 |
Ofcourse this works.
Its how we made demos in 1987..
open border:
irq=line $80
ldx #7
.dex
bne .
nop
nop
nop
ldx #4
dec $d016
inc $d016
nop
..nop
bit $fc
nop
dex
bne ..
...
...
...
adjust the first ldx
adjust the 2nd ldx
adjust the number of nops
keep fiddling until it works
Not so hard afterall :) |
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algorithm
Registered: May 2002
Posts: 705 |
can do an inc at the right moment on a badline to stabilise? or force a badline (which may produce garbage) |
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Testa
Account closed
Registered: Oct 2004
Posts: 197 |
well i didn't know that it is possible to get the damm thing stablelized with four sprites on a rasterline with some read/mod/store instuctions.. i found a thread about this topic now... but thanks...
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