Actually, I just tried recompiling the 2.4.27 kernel (it took 5 hours!) with a similar configuration to what I had with 2.4.18 and it still doesn't work. It seems that the 2.4.27 linux kernel doesn't recognize the SIS5513-based IDE device on this old computer. I guess I'm going to have to continue to use the 2.4.18 kernel.