[Toni Wilen]

I finally did some tests with OCS Denise and as usual I was wrong..

horizontal diwstart 0-1 does not normally work (just like ECS Denise) but it seems horizontal diw does open if vpos is between 0 and 8 (inclusive)

Unfortunately logic analyzer is not connected to OCS Denise Amiga so I can't really be sure which lines have special behavior. (and why?)

More tests to do..

[few more tests done]

It looks like at least one line (8? 9?) counts to 445 (not 455) because changing diwstop hpos from 0xBE to 0xBD during this line (and then in next line to 0xC8 or larger) causes display to blank.

455 - 445 = 10 / 2 = 5. Hmm..

[and some more test]

I created copper list that moves hdiwstart so that it never matches (wait for 1/3 of scanline, hstart=2, wait for 2/3 of scanline, hstart=middle of scanline and so on..)

Test 1: line 1: make sure hdiw is open by setting hstrt to some normal value, hstop=0xff, wait 1-7 lines, run above copperlist: no display

Test 2: same but wait to line 9 (or more): hidw open, visible display

There is something weird happenin on line 8 (or all lines 0 to 8)

[4th]

Same tests with ECS Denise and no more weirdness, hdiw won't mysteriously close during early raster lines.