Setting text mode in the console

[Cruncher]

Anybody know whether and how I can set text modes in the console?  I'm running woody, on a Pentium 200 with ATI Mach 64 chipset.  I've installed svgalib, svgatextmode and fbset but I can't see how to change my text mode from 80x25.   I've put vga=ask in the boot script (or whatever you call it) which gives me available modes - which I can select during the boot process and which work momentarily, but then linux continues to load and resets the mode back to 80x25.   Why do I want to do this?  I'm running prboom and quakeforge (nq-sdl) in textmode, and I want higher resolution...   - C