[XFree86] Setting up a virtual display larger than video memory?

I'm running Debian Linux on an old machine with a video-card with one meg on it. I'd like to keep running it in 16bit color, but the best I can do with that limited memory is 800x600. If I try to add Virtual 1024 768 (or higher dimensions) it gripes that (--) SVGA: chipset: tgui9680 (--) SVGA:

[XFree86] Mapping a frame-buffer for a larger virtual display into a 1meg card?

Greetings, I've got a Trident 96xx series card and an older Multisync][ monitor which seems to work fine for basic purposes (in either 800x600x8 or 640x480x16). The trouble is that it looks like it's only got 1 meg of video memory on the card, and many apps want at least 800x600x16. I've got