Re: No PETs allowed demo...

From: Olaf Höhmann <>
Date: Thu, 16 Dec 2010 22:15:47 +0100
Message-ID: <>
hi there,

andre redirected me to here... i'm the coder of the no pets allowed demo...

Anders Carlsson
no you don't mix up things. robin has a 60hz pet. i did a special version for 60hz to check if the entire stuff is working... since i don't have a pet and i could not find someone with a 50hz pet...

the demo works fine on a 8032... theoretically... maybe i'll do a 8032 version isn't too much work... only the intro and the endpart needs a 4032 since i scroll the entire screen by changing the hardware registers... on 8032 you have 2 kb this will show some crap... the 4032 mirrors the screen if it runs out of memory bounds.

Cameron Kaiser:
have a look to the zip file of the demo... there is a source included to setup this mode... there is also an assembly switch for 60hz :)

Steve Gray
the height is set to 3 lines by the way... otherwise you will not reach the 50 or 60 hz

as you can see on andre's site... the formular for the timing is
r9 char height
r4 lines total (max 127)
r5 adjust (max 31)


1+1*127+1+31 = 287 lines... but you need 400 on a 4032 (50hz) even on
60hz with 333 lines it's too less... the vsync will be too fast
this is why i choosed 3 lines for each char...

good idea @8296... i did a quick test looks like this in vice:
here i set the char height to 2...

it has a resolution of 256*125 in 2*2 res on screen...(as you can see there is a small bug at the end of the screen... didn't traced down yet) anyway was just a test to show how it looks like...

the test is for a 60hz 8296.. on 50 hz it will not work i think because
with a char height of 2 you will do not reach 313 lines...

find the prg file here:
not sure if this works on a real machine... because i don't have
roms for a 60hz 8296 so the values were found by using the 8032 50hz and changing them to 60hz... if someone can send me a 60hz rom i could do better version so far is this not working ;)

source is included here:
and orbglassc.raw
assembles with dasm..

of course with a special charrom it would be 512*125... quite heavy ratio for the pixel size. i didn't tried this yet...
but would have the advantage that the errors produced due to the not 100% fitting commodore chars will be gone...

robin asked me for a 60hz version... maybe i'll do one over xmas... due to the less cycles to use on 60hz the efx will be smaller otherwise the efx are dropping to 2 vbls...

greetz ultra ;)
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Received on 2010-12-16 22:00:15

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