Plastron Posted May 1, 2004 Share Posted May 1, 2004 Anyone still playing with the 8-bit for programming and want filcker free screens without a VBI routine here is the trick i used all thoes years ago use the interal clock think it was $14 #20 LDA with it and compare it with its self then BEQ back tp the LDA do this first before and screen action and you will get a flicker free change. Quote Link to comment Share on other sites More sharing options...
analmux Posted May 2, 2004 Share Posted May 2, 2004 hmm, I would say that is cheating. The counter on address 20 is updated by a VBI!!! Quote Link to comment Share on other sites More sharing options...
Plastron Posted May 2, 2004 Author Share Posted May 2, 2004 Cheating or not it works perfrectly and you get no ficker and is much more simple to do than a VBI call all my games used this way. Andy Quote Link to comment Share on other sites More sharing options...
Plastron Posted May 2, 2004 Author Share Posted May 2, 2004 Cheating or not it works perfrectly and you get no ficker and is much more simple to do than a VBI call all my games used this way. Andy Quote Link to comment Share on other sites More sharing options...
miker Posted May 2, 2004 Share Posted May 2, 2004 OK - i have one: To increase raster time you should buy bigger monitor Quote Link to comment Share on other sites More sharing options...
samurai Posted May 3, 2004 Share Posted May 3, 2004 wow ..that's a wisdom greetz miker Quote Link to comment Share on other sites More sharing options...
tebe Posted May 3, 2004 Share Posted May 3, 2004 best interlace (by Stanley - XLPaint) 1st: line1(screen1[0]) line2(screen2[40]) line1(screen1[80]) line2(screen2[120]) line1(screen1[160]) line2(screen2[200]) ... 2nd: line1(screen1[40]) line2(screen2[0]) line1(screen1[120]) line2(screen2[80]) line1(screen1[200]) line2(screen2[160]) ... flip 2 screen with ANTIC: antic1 dta b($4e),a(screen1) dta b($4e),a(screen2+40) dta b($4e),a(screen1+80) dta b($4e),a(screen2+120) ... dta b($41),a(antic2) <----- wait 1 frame, jump to antic2 antic2 dta b($4e),a(screen1+40) dta b($4e),a(screen2+0) dta b($4e),a(screen1+120) dta b($4e),a(screen2+80) ... dta b($41),a(antic1) <----- wait 1 frame, jump to antic1 Quote Link to comment Share on other sites More sharing options...
analmux Posted May 3, 2004 Share Posted May 3, 2004 If you really don't want to use a VBI routine, then it is a clever trick. But IMHO programming a VBI routine is too easy, and running a compare & wait loop wastes a lot of usable CPU time. Another trick by the way is checking the vertical line counter. Then you don't need any DLIs or VBIs and you can time processes at places on the screen that are independent of the Display List. I know there's some ABBUC intro that makes use of this technique only. Very clever but weird programming. To go on: When you set a pokey timer on 50 Hz you can make use of a Timer IRQ. When you synchronize the triggering of the IRQ at top or bottom of the screen, you've got the same effect. No VBIs used, rather complicated and clever. Quote Link to comment Share on other sites More sharing options...
ndary Posted May 3, 2004 Share Posted May 3, 2004 yes i wanted to say nice trick not to use VBI, bout wouldnt you use cpu time!?.. i mean wouldnt you save cpu time if you do use a VBI! Quote Link to comment Share on other sites More sharing options...
Plastron Posted May 4, 2004 Author Share Posted May 4, 2004 Well try it and see what you think Plastron the game and everything else i did used this simple trick. I found it by accident when i first stated coding and wanted to make a PMG run at the right speed and noted that it did not flicker. Eversince i used it before any screen call. Never had a problem with CPU time. One thing to avoid as i am sure you know is the branch instruction a good way to speed code is duplicate it rather than branch. This was used a lot on the ST for scrolling screens. Quote Link to comment Share on other sites More sharing options...
Tezz Posted May 4, 2004 Share Posted May 4, 2004 plastron One thing to avoid as i am sure you know is the branch instruction a good way to speed code is duplicate it rather than branch. This was used a lot on the ST for scrolling screens. That's a good tip to remember Andy. Nice one. My brother coded many demos on the ST back around 89-90 so I'm sure he will know that one!! Quote Link to comment Share on other sites More sharing options...
Wrathchild Posted May 4, 2004 Share Posted May 4, 2004 Hi, can you tell us a bit about its development? I recall chatting with Steve G. at an Atari show at the Novatel in London years ago... not long after Plastron was out (or it may have even been released at the show, I can't recall?). After commenting how close it looked to the game "MetroCross" he grinned Quote Link to comment Share on other sites More sharing options...
Heaven/TQA Posted May 5, 2004 Share Posted May 5, 2004 tezz... for which crew did your brother coded demos? all...to be honest... i don't know what's so "hightech" in this method? polish coders use this since i was born... i personally use the 540-trick... 540 will be decremented by OS every VBL so you can do this as well jsr wait wait lda #1 sta 540 wait0 lda 540 bne wait0 rts ok...it's not so compact and confortable... and if you switch off complete the OS and install your own kernel routines (NMIs, DLIs service routines) i am not sure if the "20" trick still works... the 540 definitly not if you not implement a "DEC 540" in your VBL service routine... Quote Link to comment Share on other sites More sharing options...
Tezz Posted May 5, 2004 Share Posted May 5, 2004 Heaven/TQA tezz... for which crew did your brother coded demos? Hi Heaven, we were in a small crew called PAW back then on the ST scene. We had some demos and intros out but we were never that well known I don't think. Probably the most popular demo we did was the Roger Dean demo (Roger Dean was the guy who did fantasy artwork and did some pics for Psygnosis) It was basically an intro with some ripped Mad Max music borderless with many scrollers and raster effects. The Roger dean pics were done in Spectrum 512 format. I was the gfx member. Good old Degas Elite! actually D-Paint on the Amiga was my favourite.. Don't know where the other members are these days, not seen them for about 10+ years now.. Anyway, best leave this stuff for the ST forum!!! jsr wait wait lda #1 sta 540 wait0 lda 540 bne wait0 rts Another method to remember!!! Tezz Quote Link to comment Share on other sites More sharing options...
Plastron Posted May 5, 2004 Author Share Posted May 5, 2004 i never said ti was new but it was less code heheheh wait lda 20 cmp 20 beq wait rts only 4 lines 20% saving in coding lol Quote Link to comment Share on other sites More sharing options...
Dracon Posted May 5, 2004 Share Posted May 5, 2004 Hiya Andy! Did you read my interview with Steve Goss? There was also a question about "PLASTRON"... Just check out this forum - it's still there. Are you gonna do anything else for Atari 8-bit? Quote Link to comment Share on other sites More sharing options...
mikey Posted May 6, 2004 Share Posted May 6, 2004 ok...it's not so compact and confortable... and if you switch off complete the OS and install your own kernel routines (NMIs, DLIs service routines) i am not sure if the "20" trick still works... No, it doesn't. Shadow registers are not updated when OS is off. But you can synchronize with e.g $d40b then, it is a hardware (not shadow/OS) register so works even when OS is off and most importantly in case of VBL it's updated by ANTIC. Like this: lda $d40b bne *-3 Effect is the same, waits for a hardware VBL phase. 50/sec. As accurate as "20" trick. Just my 2 cents. Peace Quote Link to comment Share on other sites More sharing options...
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