First, what board do you have?

Second, are you able to do some benchmarks on your own?

It's Shuttle HOT-419.

I suppose I could do the benchmarking, but I am currently out of 128Kx8 SRAMs so was hoping someone already checked that.

My expectation is that the bigger cache should win supposing it is able to maintain the same L2 timing as dual-bank (which shouldn't be taken for granted).

How much ram do you have ? 256K can easily cache 64MB or more of ram assuming the TAG is big enough. I doubt you will see more than a few percent difference in most benchmarks between 256k and 512k cache on a 486 limited to 128Mb ram. As far as single bank versus dual bank cache: I do not think you will see much difference, about same as using one main memory bank versus 2 on a 486, just my opinion....

@Horun, if you are able to enable dirty bit inside the existing tag chip (in contrary to adding a dirty cache chip), then it cuts the cached memory into half - 32MB.

At the same time, having 4x32MB 72pin simms in such machine is easily achievable and maybe even desireable. (The uncached top part of ram can be used as ramdisk)