I have two original Compaq Portables, both of which are giving POST errors when they boot which indicate bad RAM. I have gone through a few rounds of swapping RAM chips between the machines to identify the bad chips, but have come up against a potential roadblock. My problem is that there are a number of different chips used in the machines. As I don't have any data books on these chips, I am not sure if the different numbers are simply different manufacturer's numbers for the same chips, if some of the numbers are simply date codes, or if they are really different, incompatible chips. If someone is familiar with these numbers, or can look them up for me, I would really appreciate it: Chip #1: Hitachi 1818-3006 Japan 8332U HM4864P-3 Chip #2: NEC 8539PF513 D41256C-15 Chip #3: Fairchild (I think; has an "F" with a bar above and below it) MB81256-15 8548 M79 BC Chip #4: NEC 8538PF532 D41256C-15 If you could let me know the size of each chip, as well as the width of the memory, it would help me determine what size of RAM I should be setting the motherboard DIP switches for. Also, would I be correct in assuming the "-15" appearing on most of the chips specifies 15ns? If anyone is familiar with adding RAM to the motherboard on the Compaq, I would appreciate your input on the following: The machine has 4 banks of RAM, consisting of 8 chips each, plus 1 chip for each bank marked "BIT 0". The first two banks of chips (0 & 1) are soldered, the other two (2 & 3) are socketed. 1) Is the "BIT 0" chip a parity chip? 2) Can RAM be installed in Bank 2 without having to populate Bank 3? Any help in regards to the above is much appreciated!! Thanks in advance.