Bringing a recalcitrant SiS ethernet adapter up

I have a SiS900 Ethernet controller that I could assign IP and IPv6 addresses to, but I couldn't bring it up. mii-tool reported that the link was negotiated, and it had worked before my recent kernel compile.

I tried everything I could think of, and recompiled the kernel over and over again. Finally I realized that the other thing I'd changed was turning off SMP support - I turned it back on, and it worked! I think that the card was in INT 19 or something, and I needed SMP support to reach those higher interrupts, even though I had a single core CPU.