VGA VRAM Wrap

Discussion of development and patch submission.
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Mills
Posts: 14
Joined: Thu 28 Sep, 2017 9:29 pm

VGA VRAM Wrap

Post by Mills » Sat 24 Nov, 2018 5:44 pm

Hi, Thanks again for this great emulator.

I think the VGA VRAM is not wrapping correctly on mode 13, (the one with only 64 Kb).

Well, it wraps, but It always thinks the vram is 256 Kb (mode X) and I have to scroll 4 pages down until it reaches address 0 of VRAM again.

Here you see a screenshot from Dosbox (it works the same on real PC), and a screenshot using PCem, Also include a test program.

Thanks a lot.
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Mills
Posts: 14
Joined: Thu 28 Sep, 2017 9:29 pm

Re: VGA VRAM Wrap

Post by Mills » Sun 25 Nov, 2018 9:51 am

Well the code was tested it on a real VGA, and PCem is working OK. So that's not a bug, it just does not wrap around 64 KB but 256 Kb.

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SarahWalker
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Posts: 1726
Joined: Thu 24 Apr, 2014 4:18 pm

Re: VGA VRAM Wrap

Post by SarahWalker » Mon 26 Nov, 2018 11:43 am

I suspect this varies from VGA board to VGA board. Which real board was it tested with?

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