I'm trying to increase the cache in my 486DX2-66 from 128K to 256K (which is coming from another 486 machine). The current chips are four CY7C199-20PC and one IS61C64AH-15N. The chips I'm replacing with are eight IS61C256AH-20N and one IS61C64AH-15N. I've got jumpers on the MOBO with 64K, 128K and 256K. With the 256K chips in place and the jumpers set, the computer starts OK with the memory test and then the usuall "wait..." message and then locks up. The 256K works in the older, slower 486 machine but not the newer, faster machine. The MOBO has a CONTAQ/5 chipset with AMI BIOS. Is there something I'm missing or am I reading my cache chips wrong? tia.... Winston