Western Digital Graphics Card \ VOGONS

Western Digital Graphics Card

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First post, by b_rros

Posted on 2014-01-31, 11:59

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Hi, I got a new old PC, it is an old 486 with a DX2-66 processor, the case is filled with rust so I will have to deal with that. But right now I would like to know a little bit more about the graphics card, it's a Western Digital card (I didn't even know that WDC made graphics cards) with some kind of dip switches on the back, does anyone know what those switches are?

Reply 1 of 8, by Auzner

Posted on 2014-01-31, 13:09

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Just a guess, but the switches are probably for toggling between NTSC/PAL video mode. It could be that an RCA CVBS output is on those pin headers.

Reply 2 of 8, by Old Thrashbarg

Posted on 2014-01-31, 16:26

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Just a guess, but the switches are probably for toggling between NTSC/PAL video mode. It could be that an RCA CVBS output is on those pin headers.

That's... not even anywhere in the ballpark.

The switches are for setting the refresh rates for the various resolutions. The pin header is just a regular VESA feature connector. Here is a complete description of the various settings.

Reply 3 of 8, by Stiletto

Posted on 2014-01-31, 16:38

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Old Thrashbarg wrote:
Just a guess, but the switches are probably for toggling between NTSC/PAL video mode. It could be that an RCA CVBS output is on those pin headers.

That's... not even anywhere in the ballpark.

The switches are for setting the refresh rates for the various resolutions. The pin header is just a regular VESA feature connector. Here is a complete description of the various settings.

And here is the datasheet for the WD90C31A video controller (well, the WD90C31):
http://www.vgamuseum.info/images/stories/doc/wd/wd90c31.pdf

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Reply 4 of 8, by Auzner

Posted on 2014-01-31, 16:42

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Then I actually was in the ballpark, since NTSC and PAL are different refresh rates.

Reply 5 of 8, by keropi

Posted on 2014-01-31, 17:18

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Auzner wrote:
Then I actually was in the ballpark, since NTSC and PAL are different refresh rates.

Not really, there is also different color encoding, timing , blah blah blah. PAL/NTSC is not just a 50/60hz difference. But that's not for discussion here...

The switches are indeed for selecting refresh rates in higher resolutions as well as selecting to have them interlaced.
What is interesting is the fact that there are 2 WD chips on this VGA, what do they write on them? One is the WD90C31A and the other? It could be a case that one is an accelerator for high-res stuff

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Reply 6 of 8, by b_rros

Posted on 2014-01-31, 17:25

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In this article http://books.google.cz/books?id=rT0EAAAAMBAJ& … WD90C31&f=false they do talk about a Windows accelarator, maybe that's it.

Reply 7 of 8, by Old Thrashbarg

Posted on 2014-01-31, 18:15

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That second chip is probably just for the VLB interface... IIRC, the 90C31 didn't natively support local bus.

The 90c31 was an 'all-in-one' chip with both standard VGA and acceleration functions built-in, similar to the ET4000w32 and Cirrus 542x series. It was a pretty decent performer for its time too, so it wouldn't have needed a second accelerator chip.

Reply 8 of 8, by Alegend45

Posted on 2014-01-31, 19:03

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I actually have a 286 motherboard with a WDC 90c00. I'm gonna want to write some code to emulate it in MESS, or something at some point.

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