Search found 4 matches

by VileR
Tue 15 Jan, 2019 6:59 pm
Forum: General
Topic: CGA mode select register (3D8h) inaccuracy
Replies: 7
Views: 3181

Re: CGA mode select register (3D8h) inaccuracy

Brilliant, much obliged.
by VileR
Sun 13 Jan, 2019 8:08 pm
Forum: General
Topic: CGA mode select register (3D8h) inaccuracy
Replies: 7
Views: 3181

Re: CGA mode select register (3D8h) inaccuracy

Sorry for taking a while, but here' s a program that at least checks for issue #1 described above. It shows a test screen for 4 seconds - the +VIDEO bit in the Mode Control register is cleared after the first row of text, so nothing should be visible below it.   RASTTEST.zip   Left: results in PCem ...
by VileR
Wed 02 Jan, 2019 9:56 pm
Forum: General
Topic: CGA mode select register (3D8h) inaccuracy
Replies: 7
Views: 3181

Re: CGA mode select register (3D8h) inaccuracy

Maybe the same that happens here http://pcem-emulator.co.uk/phpBB3/viewtopic.php?f=3&t=500 Hmm, nah- that thread seems to be about composite color reproduction (unless I'm missing something)... this is unrelated. Actually, the issues I mentioned above don't matter for any game/demo that I know of, ...
by VileR
Wed 02 Jan, 2019 4:30 pm
Forum: General
Topic: CGA mode select register (3D8h) inaccuracy
Replies: 7
Views: 3181

CGA mode select register (3D8h) inaccuracy

While playing with some display-related code I noted a couple of discrepancies between PCem v14 and the real hardware. Both have to do with CGA register 3D8h, specifically bit 3 (+VIDEO): If this bit is modified in mid-frame, on an IBM CGA board the change takes effect immediately (at the current be...