Earlier quoted context omitted.
That's not cache, friend - that's main system memory =) (and 640 KB by the time of the 486) (though, speaking of cache, the 486 was the first chip in the family to have L1 cache - a whole 8KB of it!)
Parent specified a board with SIMM sockets, which would contain main memory. The 486 family supported external L2 cache, for which 64KB would be a plausible size.
Did SIMM RAM straight up replace the DIP chips when it was introduced? For some reason I thought they were used in parallel, with conventional RAM physically separate from the rest. I guess there's no reason that should have to be, though, as the 640K barrier was a real mode limitation, and nothing more. What they say about assumptions applies.
I guess I kind of missed out on the fun here, going straight from an XT to a Pentium...