I have a bunch of middle-aged motherboards (386 & old 486) that have these 28 pin 300 mil dip packages and no datasheets. I've searched extensively for datasheets on the web to no avail. Typical part numbers are PDM41256SA20P from PARADIGM; HM3-65764H-5, etc... I'd really like to hook them up to PICs for external memory but I don't know how they work. Anybody familiar with these plentiful but mysterious chips?