So this initially started when I realized I was mixing a 256MB ECC PC100 stick and a 256MB non-ECC PC133 stick in my K7V, yoinked them out, rediscovered the 1GB PC133 stick I got for this thread while perusing my stock of RAM for a matching set (ideally PC133 256MB), and decided I might as well try it. One stick install later:

1GB seen. So this motherboard has 1GB support, nice. But I have a couple 512s too, so what happens if I plug them in? I plugged them in and... sirens. Tried different configurations. Sirens. The memory sticks I was just using. Sirens.
The processor had slipped out since I'm only on one retention clip, the other broke on me. Push that in, turn on with 1G+512+512, and...

The math checked out.
I don't have more than that one 1GB module unfortunately, I wish I did so I could test if it can see 3GB. That it sees 2 is a pretty good sign, though. My bad if this is common knowledge and I'm the last person on Earth to figure this out, I did a search and see 2GB being referred to with Athlon XPs at the earliest. I'm probably going to drop it back down to 512MB since I believe memory interlacing requires only two of the three slots populated, but who knows?
If only the K7 supported DDR, that'd be really nice to have had.