S3 938 Issue - Incompatibility with scrolling games \ VOGONS

S3 938 Issue - Incompatibility with scrolling games

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First post, by Necronomfive

Posted on 2025-03-31, 18:40

Necronomfive Offline

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Hi,

I have just acquired a #9GXE ISA card, which has 2MB of VRAM and 1MB VRAM, euipped with the S3 928 video accelerator.

While the card performs most formidable in standard applications and also high-resolution output in Winfows, it seems to be buggy when starting scrolling games, like Jazz Jackrabbit. The issues manifest in single garbage lines, which seem to be read from different memory locations.

Is that a known issue with the S3 928? I specically picked that card, because my previous experiences with thrir chips have been very positive - Virge, Trio 32 and Trio 64 dont have issues with hardware scrolling.

Thanks for your help!

Reply 1 of 3, by clb

Posted on 2025-04-01, 19:27

clb Offline

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I'd be curious to hear what the results are if you download SCROLL.ZIP from https://github.com/juj/crt_terminator/tree/main/DOS/bin and run it on the adapter. Which scroll methods look smooth on that card?

See also this thread: Why does Commander Keen 4-6 hardware scrolling glitch on ATI (Mach) PCI video cards? . The comment in Re: Solved(?): Why does Commander Keen 4-6 hardware scrolling glitch on ATI (Mach) PCI video cards illustrates what the behavior on different adapters is. If you compare against that table, note the details in the help text in the screenshot, since the version of SCROLL has changed since then.

Exact details of hardware scrolling on VGA adapters was something that vendors relatively easily got "wrong" (here wrong means "different than original IBM VGA", although one can argue that the original IBM VGA behavior was flawed to begin with)

Reply 2 of 3, by keenmaster486

Posted on 2025-04-01, 20:17

keenmaster486 Offline

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Check the compatibility matrix here: https://gona.mactar.hu/DOS_TESTS/

Looks like that's a known issue with these cards. Btw you have a typo in your title: 938 should be 928.

World's foremost 486 enjoyer.

Reply 3 of 3, by Necronomfive

Posted on 2025-04-04, 12:32

Necronomfive Offline

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Joined: 2024-03-25, 10:18

keenmaster486 wrote on 2025-04-01, 20:17:

Check the compatibility matrix here: https://gona.mactar.hu/DOS_TESTS/

Looks like that's a known issue with these cards. Btw you have a typo in your title: 938 should be 928.

Thank you for your help, that‘s a really comprehensive list! Wish I had known about this list beforehand, but at least I know now that my replacement card with CL-GD5434 wont give me any issues here.

Yeah, it‘s a typo, the chip is an S3 928. Lesson learned: never assume compatibility parity amongst different generation of chips by a single vendor. 😉

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