Druid: Dæmons of the Mind \ VOGONS

Druid: Dæmons of the Mind

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First post, by Gamecollector

Posted on 2012-04-25, 11:11

Gamecollector Offline

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Rank: Oldbie
Posts: 1413
Joined: 2010-10-06, 22:17
Location: RU

I found the cd with this game in my old garbage...
Installed, worked (yeah, the mind and body points are restoring with the time! 15 years ago I don't know this and call this game "unplayable" 😀 ).
The only trouble is - all of the movies in-game have 3 black lines. Not critical but very annoying.
I don't have my DOS PC anymore (rest in peace, the old and honored Pentium), so I can't tell the source of this - DosBox or the cd itself.
Any Ideas?

P.S. DosBos 0.74, P4 3.00E/Radeon X850 PE Agp/Windows Xp Pro Sp3.
With the Ykhwong's build the lines are still here...

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Reply 1 of 4, by ripsaw8080

Posted on 2012-04-25, 15:40

ripsaw8080 Offline

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Rank: DOSBox Author
Posts: 5034
Joined: 2006-04-25, 23:24

According to wd, this is a known issue caused by the use of segment limits, a CPU/paging mechanism the DOSBox devs have decided not to emulate for performance reasons. This case is a relatively minor glitch compared to a few others caused by segment limits.

Reply 2 of 4, by peterferrie

Posted on 2012-04-25, 16:53

peterferrie Offline

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Posts: 649
Joined: 2008-05-08, 21:54

Yes, that's exactly the problem.
I was working on a patch for it last year and never finished it.
Perhaps I will look at it again.

Reply 3 of 4, by Gamecollector

Posted on 2012-04-26, 17:56

Gamecollector Offline

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Rank: Oldbie
Posts: 1413
Joined: 2010-10-06, 22:17
Location: RU

Tnx for the info.
Yes, no lines in the VirtualPC+MSDOS 6.22 setup...
Oh, well...

Asus P4P800 SE/Pentium4 3.2E/2 Gb DDR400B,
Radeon HD3850 Agp (Sapphire), Catalyst 14.4 (XpProSp3).
Voodoo2 12 MB SLI, Win2k drivers 1.02.00 (XpProSp3).

Reply 4 of 4, by TheGreatCodeholio

Posted on 2023-08-31, 21:12

TheGreatCodeholio Offline

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Posts: 815
Joined: 2011-08-18, 20:15
Location: Seattle, WA

This issue was brought up in the DOSBox-X issue tracker and I have an analysis of what is causing the black lines.

The game is not using any segment limit or page fault tricks. Instead when copying scanline by scanline to video memory it seems to rely on a quirk with SVGA bank switching where the 128KB VGA memory area 0xA0000-0xBFFFF allows you to write to 0xA0000-0xAFFFF (the 64KB bank you switched to) and to 0xB0000-0xBFFFF (the next 64KB bank). If you don't emulate that, then the remainder of the scanline going past the 0xA0000 bank is lost and therefore black lines.

https://github.com/joncampbell123/dosbox-x/issues/4384

DOSBox-X project: more emulation better accuracy.
DOSLIB and DOSLIB2: Learn how to tinker and hack hardware and software from DOS.

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