Kernel compilation time and hardware limitations

Recompiling the Linux kernel seems to take longer than I would expect. I've switched from a 233MHz processor to an 850MHz one, but the process doesn't seem to be going even twice as fast. So I'm wondering what's the most likely limiting factor in my system. The critical parameters: 850MHz Athlon Tyan S2390 motherboard 256MB PC100 memory 30GB 7200 RPM hard drive I assume that nothing else is likely to be relevant. Paul