Hi, I have a Dell laptop. Pentium M 1.6 ghz, 512mb RAM, integrated Intel 915 graphics running XP.

I have a Mac, Core 1.5 ghz, 2.0 gb RAM, integrated Intel 950 graphics.

Despite showing similar tdem demo1 scores, while playing online I notice the Dell has consistently higher average fps, and significantly higher max fps (80+ vs 50).

I know the Windows version is better optimized, but I also noticed that when Nexuiz loads on the Dell almost all of the OpenGL routines are disabled.

I am wondering if I can run the OSX client in software rendering mode? Thanks

No, the engine has no software renderer.

OK... well then how can I disable the OpenGL extensions that get loaded at startup that I see in the console?

Either by separate command line options (see darkplaces.txt in the source tarball), or by specifying the command line option -safe for testing (which disables ALL of them).

At my current config:

demo2 -safe: 25 60 122
demo2 +r_glsl 0: 27 61 117
demo2: 38 69 118

So even though I am using options that are not exactly trimmed for speed (like r_glsl_contrastboost), curiously GLSL is still faster than non-GLSL rendering here... and -safe seems to disable at least one extension that makes rendering FASTER here than without -safe (even when r_glsl 0 is specified, which is also implied by -safe).

start with the option -safe that disables all extensions altogehter.
As the readme does not seem to mention this one..