Video Card Implimentation?

Post: #1
I've been trying to learn what I can about making OpenGL work, and browsed the ATI website for a little more information on the Rage 128/Pro. One of the pages said that the framebuffer should be used at 32 bit color, since that's how the card runs, and even though that requires twice the memory as 16 bit color, the card can handle up to 32MB for the buffers.
I've always been thinking that the Rage cards had 4-8 MB of VRAM -- so how does this work, what do the numbers mean, and how can I utilize this?
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Post: #2
Rage 128 cards had 16MB of memory. Rage Pro cards had 2-6, depending (Original iMacs shipped with 2MB and a slot, rev. B had the extra 4MB already installed, soon after that they went to 8MB and then Rage128 with 16MB). Rage Pro is virtually a non-starter. Both are PCI, so bandwidth limited.

16-bit colour looks atrocious on these cards, but yes, you have more room for textures (not much, but it helps). 800x600x2bytes = ~ 1MB per buffer, or 2MB per buffer at 32bit. Clearly you are limited in the textures anyway on a 16MB or 6MB card, but changing the colour depth on the Rage128 doesn't get you much more memory, and it has almost no effect on the fill rate -- ATI cards have always been tailored to 32bit colour mode, unlike nVidia and Voodoo cards of similar vintage.

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Joined: 2002.04
Post: #3
Minor correction: most Rage128 cards only have 8MB of video memory. A few of the later model iMacs and some of the G4s have 16.

Don't forget to include the depth buffer when you try and estimate how much VRAM your context will take up.
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Jeff Binder
Post: #4
The Rage 128 that came with my Blue and White G3 had 16 Megs as well. I've seen Rage 128s with 32, although I don't know if any of them were available for Mac. I know no Macs came with such cards built in.
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