My Socket 7 retro machine has an MSI 5128 v1.1 motherboard in it like documented on https://stason.org/TULARC/pc/motherboards/M/M … MS-5128-VE.html. I came to the possession of an COAST module in the idea of upgrading the machines L2 cache from 256k to 512k.

The module fits and the machine boots when installed. Much to my surprise the final BIOS screen right when the OS starts shows 0 kb cache when the module is installed. It looks like the plugged in COAST module disables the onboard cache instead of expanding it.

According to the manual (ftp://retronn.de/driver/Mainboards/MSI%205128/) the COAST module must comply to COAST spec 1.3. On the module itself is a printing "Rev 1.3" which leads me to belive the module should be compatible. The statson page mentions an JS1 jumper to switch between 256k and 512k cache configuration but this jumper is nowhere to be found on the board. Am I missing something?

Unfortunately this board is the only one I own which has a COAST socket so I cannot check if the module itself is okay.