OKS advertised the Multi-Kache cards as having 256k expandible to 1mb.
I was looking at some pics of the Multi-Kache cards and noticed something, 18 and 20 pin RAM.
In the pics one card has HM511000P-10S which is 1mb x 1bit. While the other card has AAA1M204P-08H which is 1mb x 4bit. That seems to indicate that the card can have 4mb cache.