Jerky motion on ATI cards: possible community fix?

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Jerky motion on ATI cards: possible community fix?

Post by keenmaster486 » Wed Jun 01, 2016 16:01

We all know about the "SVGA compatibility" and "Fix jerky motion" options in the Keen Galaxy menus.
But these do nothing to fix the jerky motion and scrolling glitches on ATI video cards, which are common on retro DOS computers.

One thing I have noticed, however: Keen Dreams, and therefore Atroxian Realm and cksrcmod, are devoid of this jerky motion bug.

So I want to know the following:

1. Why does the Dreams codebase not have that ATI incompatibility?
2. Can we compile new executables using cksrcmod for Keens 4, 5, and 6, to fix the jerky motion bug for good?

I've been mulling this over in my mind for a while, ever since I built a retro DOS computer with an ATI card and ended up banging my head on the table because it's incompatible with Keen.
But then I discovered that Atroxian Realm works on it, so I had fun playing that for a while :p

So is anyone else interested in fixing this?
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Post by Keening_Product » Thu Jun 02, 2016 0:14

You've probably looked into this already, but is there a more recent display driver you could use? I'm not sure what options there are for such things in DOS, but there might be a fix there.
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Post by keenmaster486 » Thu Jun 02, 2016 2:20

Well, there's no such thing as a DOS display driver. That's all program-specific, which is why Keen Galaxy can choke while Keen Dreams doesn't.

And as for display drivers in Windows, it doesn't matter what you use there since DOS programs get direct hardware access.
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Re: Jerky motion on ATI cards: possible community fix?

Post by kvee » Thu Jun 02, 2016 8:10

keenmaster486 wrote:jerky motion and scrolling glitches on ATI video cards
Jesus man, I'm usually not the one to start a flamewar, but this almost asks for it :D

On a serious note, let's try to get to the bottom of this. Could you post full specs of the system + your config.sys and autoexec.bat?
Also a video capture (recording screen with phone would be enough) should confirm that I probably have no idea what to do, but the one thing that would be worth trying is measuring vblank times on the card (that I should be able to help with) - jerky motion would indicate inconsistent frame timing and i do have a potential fix in mind.

Also, did anyone research what "fix jerky motion" does? Maybe I've got the same idea :D

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Post by BlueGasMask » Fri Jun 03, 2016 3:33

Interesting, I'm running an ATI XPRESS1100 and have this problem myself!
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Post by Levellass » Fri Jun 03, 2016 11:17

*Gives Dosbox a cookie*
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Post by keenmaster486 » Sun Jun 05, 2016 18:51

OK, first the video:

:p Click here for professionally shot and edited video! :p

It's doesn't look pretty but you can see the glitching pretty well. And this happens no matter what the combination of SVGA Compatibility and Fix Jerky Motion.

As for system specs, it doesn't matter what they are, you can have any combination of EMM386, QEMM, HIMEM, various TSRs, mouse drivers, etc.

The video was shot using a stripped-down floppy disk booting with the following config:

CONFIG.SYS:
DEVICE=HIMEM.SYS
DEVICEHIGH=EMM386.EXE
DOS=HIGH,UMB

AUTOEXEC.BAT:
@ECHO OFF
A:
CD\
CLS

Totally stripped down and basic. But like I said, this glitch happens no matter what PC you're using and what configuration you have, the only common denominator is the ATI video cards.

Also, see this: http://gona.mactar.hu/DOS_TESTS/

Scroll down to the ATI cards, and notice how every single one has "Scrolling problems" in red for Keens 4,5, and 6, but Keen Dreams is green. Apparently this also happens for various Matrox cards.
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Post by kvee » Mon Jun 06, 2016 11:50

Woah, definitely not the kind of glitching I expected!

I'm afraid I've no idea how to fix this.

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Post by Keening_Product » Mon Jun 06, 2016 15:13

Have you tried using a different version of Keen? I doubt it will make a difference, but it might.
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Post by krivulak » Fri Jul 08, 2016 8:30

I had EXACTLY same problem, but I solved it the easiest way. My 486 Gaming Rig had PCI ATI RAGE II+DVD, scrolling problem was horrible, it didn't do only the glitch you recorded, but few other glitches too. Few weeks later I noticed that we have an exposition of old stuff in computer class. So I dug out one broken TNT2 on AGP card and asked teacher, if I can swap it for something else. Few moments later I scored S3 Trio 64V+, which was little bit older, but had WAY better test results, and had NO problem with Commander Keen whatsoever! (Well, to be fair, it wasn't the first try, I tried also SIS 6326, it worked well too, but turned CK all red. Don't know how, don't know why, it just did.) Here is one interesting website that shows compatibility with quite a few games and quite a few graphics card.

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Post by keenmaster486 » Fri Jul 08, 2016 13:51

Right, exactly. The s3 trios are awesome for DOS compatibility; they'll run just about anything flawlessly. That's why it's the emulated card in DOSBox!

At this time I'm thinking that the best approach is to compile cksrcmod to work with Keens 4,5,6,etc. and be done with it, and not mess with patching.
Question: what exactly needs to be done to cksrcmod to make that work?

We don't even know what it is in the code that's causing it, all we know is that cksrcmod, AR, and Dreams are unaffected.
I flermmed the plootash just like you asked.
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