VOGONS


First post, by Durandal

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Hey guys, I've got a Dolch LPAC-486 portable PC with a corroded original motherboard that I might not be able to repair, so I'm thinking of putting a spare Pentium 166MHz board into it instead along with a Voodoo 1.

The only problem is that the LCD requires the use of a specific VGA card (connects to it via ribbon cables), and that VGA card is 16-bit ISA... How bottlenecked is the Voodoo going to be? Is this even worth doing at all, or should I use this machine only for early to mid 90's DOS games?

If I really wanted to, it would be possible to upgrade the LCD to something more modern with a standard VGA connector that would allow me to use a PCI VGA card + Voodoo in the P166 board, but I don't particularly fancy the idea of modifying the case for said modern LCD.

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Reply 1 of 7, by imi

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the voodoo card is not going to be bottlenecked by the card, but you won't have any picture from it on the LCD, when the voodoo card is used it outputs it's own signal on the VGA out (hence the passthrough if not using it).
so yeah, if you want any picture from the voodoo on the internal LCD easiest would be to replace it with another one.

Reply 2 of 7, by Oetker

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I don't understand how you want this to work, if the monitor can only be connected to that vga card, how would you even connect it to the Voodoo? And can you even connect the original card to the Voodoo using a passthrough cable?
I also don't understand your question about a bottleneck, in 3D accelerated games only the Voodoo is used. With such a setup there might a certain period of game releases where your 2D card is too slow of course, e.g. running high res Duke3D.

Reply 3 of 7, by chinny22

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You could plug a external screen direct to to voodoo. Some people do that to get around loosing signal quality using a passthrough cable.
It's hardly ideal though depending on how the games coded you may have 2D images like the menu showing on one screen then gameplay on the other screen.

But as for your question is it worth it I'd probably have to say no or at best a just as a mess around project for a day.

Reply 5 of 7, by mothergoose729

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rmay635703 wrote on 2021-06-16, 16:37:

Something I’ve never understood
Why couldn’t Voodoo cards send /receive the picture over the feature connector?

I haven't seen my voodoo cards layer images from the 2d and 3d cards. In every game I have tried it is on/off. The Voodoo cards do the menus and cutscenes in some games, and in others they let the 2d card do that.

Reply 6 of 7, by megatron-uk

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You can actually copy the rendered final frame in Voodoo framebuffer back over the PCI bus and window it, overlay it over content on the 2d display etc. The problem is that it's slow, it certainly won't be up to 60fps high speed content, but it was useful for more "productivity" purposes.

This was the way we got early hardware acceleration for OpenGL Linux in the mid 90's. I believe it was one of the first hardware targets for Mesa GL. I often wondered if anyone else exploited the hardware this way to turn a 3DFX card into a windowed rendering target rather than full screen.

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Reply 7 of 7, by Durandal

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Well that's what I get for writing posts at midnight, I completely forgot about the passthrough - problem solved then, thanks guys. 😜

I might see if I can get a friend to help me figure out how the ISA card is driving the original LCD, it may be simpler than it looks. It doesn't get power from the card, so it can only be video signals.

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