163 (H) S12/Storage Devices 25-Jul-91 22:09:10 Sb: Card drives Fm: John Feagans 75300,703 To: SYSOP*Marty Mankins 75300,1770 (X) I had the good fortune (or bad) of running across a doa Portfolio RAM card. I popped it open to see what was inside. What I found was that they were using 32k x 8 SRAM die bonded to the board. One chip =32k, two =64, four=128k. They also had a small custom chip which took care of the miscellaneous logic, address decode, power detect, power down. Die bonding means that instead of mounting the die in a lead frame and encapclating it into expoxy, it is actually bonded on the printed circuit board, wires attached to the appropriate pads, and the whole works potted in exposy on the PCB. Everything is fine as long as the yield from the chips is good. Get one bad chip on a 32k board, you just generated scrap. Get one on a 64k card you just wasted one potentially good chip. Get one bad on a 128k you just wasted three potentially good die. You get the idea how the price gets out of hand quickly with larger cards. The PCMCIA cards on the other hand use already tested bonded, and packaged parts. I also disassembled one of those cards as well. The PCB has little square holes in it where the packages rest. They were gull wing and soldered to the board. It seems that their is an additional burden of cost on packaged parts but in the long run fewer parts resulting in less cost would be used.