dth@cs.brown.edu (Dzung T. Hoang) (03/01/91)
I added 512K to my 520ST using the "piggyback" method. This worked for a while until I notice problems with the added memory. It seems that one of the memory chips likes to flip bits. I suspect that it is a refresh/ access speed problem. I am thinking of removing and replacing the problem chip, but I have no idea how to identify it. The errors always occur at a particular bit--I think it's bit 4 in a 16-bit word. Can someone post a list of "what chip number goes with what bit"? In the meantime, how do I disable the added memory from software? I remember comming across a program that configures the ST to use only the first 512K of RAM at bootup. Can someone point me to a source, preferrably anonymous ftp? I have some hints about adding memory using the piggyback method. I had lots of problem getting the computer to boot from the floppy disk until I added some buffers to the address and CAS/RAS lines. Basically, I removed the resistors that are connected in series between the address lines and the RAM chips and connected TTL buffers in between. That fixed the boot problem, but I still have the "refresh" problem. ---------------------------------------------------------------------------- Dzung T. Hoang dth@cs.brown.edu ----------------------------------------------------------------------------