AFAIK, the memory inside the Tom chip was never a cache. The bug you're probably thinking of is one that makes it difficult to run code on Tom's RISC core directly from main RAM. IIRC, jump instructions are pretty bugged when not running from internal RAM, but the homebrew community came up with a workaround. It's still not acting as a cache in that case though. It just fetches instructions from RAM as it goes.