Short display lists on real hardware?

[Sheddy]

Do really short display lists with just a few dozen scanlines before the jump and wait for vblank work without rolling on real TVs and monitors? The display list doesn't need to be padded to some minimum length?

 

They work on emulators, and "wait for vblank" gives the impression that it should, but my real Atari is packed away, so thought I'd ask first to be sure. Thanks!

[funkheld]

this loop of the mist-fpga.

it depends on the monitor ?

I have on mist-FPGA a VGA monitor.

 

greeting.

Edited September 16, 2018 by funkheld

[phaeron]

Yes, they do. The JVB instruction has no effect on display timing. It is simply a jump instruction that also sets the flag to turn off display list DMA until the next frame. This causes ANTIC to internally repeat blank mode lines ($00) until vertical blank, except without the display list fetch. It doesn't change the number of lines in the frame that the TV sees.

[Sheddy]

Ah, OK - It'll output blank lines itself. Thanks for the explanation.

[_The Doctor__]

this is true, but while antic self pads, what if any affect do we get on cpu cycle use?

Edited September 16, 2018 by _The Doctor__

[Sheddy]

Just the cycles to retrieve the display list I believe, which would be very, very minimal. It makes the code for vertically scrolling those few dozen scan lines a bit easier though. Not generally useful though.

[+Nezgar]

Just the cycles to retrieve the display list I believe, which would be very, very minimal. It makes the code for vertically scrolling those few dozen scan lines a bit easier though. Not generally useful though.

I remember appreciating Bob Puff's superArc/superunarc - CPU intensive, so made sense to blank the screen for the speed boost, but used a single text line display list to show current filename / status, which I thought was a great compromise.