Correctly setting up an interlace screen

[KONEY]

yes of course, thanks! https://github.com/KONEY/take_em_in_...lob/main/J.exe

I put MOVE.W #$8000,$DFF02A just before the copperlist is pointed, isn't it the absolute first frame? Anyway the way I did things should not need that information because one copperlist is pointing to the other, regardless. I put it because I was out of options to try ;P

[KONEY]

Originally Posted by ross

However the most important thing is that for each frame you set the pointers for the bitplanes..

EXACTLY! but is this somehow possible from copperlist?

[ross]

Originally Posted by KONEY

EXACTLY! but is this somehow possible from copperlist?

Usually not, it could only do it by use the blitter to modify itself, but that's too complex for this case...
But why not do it directly from the VBI? So you shouldn't duplicate the copper list.

I have a doubt ... which Kickstart do you have in the A3000?
EDIT: more than a doubt it is almost a certainty and would explain everything, but I'm waiting for you to tell me
Is the reason I asked you for a binary

[ross]

Originally Posted by KONEY

Anyway the way I did things should not need that information because one copperlist is pointing to the other, regardless.

I forgot to answer this.

It is not that trivial unfortunately.
The interlaced signal on a 15Khz PAL or NTSC screen must be constructed appropriately because the frame is always constructed using first the LOF then the short one.
So if you 'get off to a bad start' you may have reversed lines.
However, this has nothing to do with the other problem.

[KONEY]

OK, so here are the answers:

VBI I tried but is not consistent, if the CPU is slightly under pressure odd and even lines are swapping. And this has nothing to do with correct start because I can see them changing over time...

A3000 has 3.1 KS on ROM. So far everything I ran on it is not flickering. I also tried Shadow Of The Beast whisc has a hires laced image in the introduction, that is steady as you'd expect from a SVGA display.

I'm super curious now! what's the explanation?

[ross]

Originally Posted by KONEY

VBI I tried but is not consistent, if the CPU is slightly under pressure odd and even lines are swapping. And this has nothing to do with correct start because I can see them changing over time...

If you are under pressure, simply use a WAIT on copper list to set the bitplane pointers few lines after.
BUT with a consideration and here I link to the second answer...

A3000 has 3.1 KS on ROM.

Here is the key

Your system IRQ3 call ROM function, which in addition to possibly putting your setup under pressure, does not behave the same in all KSs.
In 3.1 at each frame it rewrites VPOSW to re-set the LOF as on system active screen.
In your case it resets you continuously for long field

[KONEY]

Originally Posted by ross

If you are under pressure, simply use a WAIT on copper list to set the bitplane pointers few lines after.

You mean something like this?

	DC.W $3441,$FFFE		; HPOS
	.BplPtrs:
	DC.W $E0,0
	DC.W $E2,0
	DC.W $E4,0
	DC.W $E6,0...

Originally Posted by ross

Your system IRQ3 call ROM function, which in addition to possibly putting your setup under pressure, does not behave the same in all KSs.
In 3.1 at each frame it rewrites VPOSW to re-set the LOF as on system active screen.
In your case it resets you continuously for long field

wait, stop... even if the OS is killed!? EDIT: I tried the same config with winuae and... you're right...

any possible workaround?

[ross]

Originally Posted by KONEY

You mean something like this?

	DC.W $3441,$FFFE		; HPOS
	.BplPtrs:
	DC.W $E0,0
	DC.W $E2,0
	DC.W $E4,0
	DC.W $E6,0...

Well, maybe better before the first visible line, like:

DC.W $2B01,$FF00

depends on when you change the pointers during your VBI routine, a few lines might also be enough, like:

DC.W $0B01,$FF00

wait, stop... even if the OS is killed!? EDIT: I tried the same config with winuae and... you're right...

any possible workaround?

Yes, OS is killed but IRQ3 is active and it point to ROM code..
Change the vector to point to your routine

[KONEY]

I'll try!! thanks!