The total 8MB has now been installed and has passed the first RAM test!(click to enlarge)
WOW! That was a bit of an ordeal and a challenge! The trickiest part was tracking down bad connections. With the chips all soldered to the adapters, it made for a VERY tight fit for some, and a connection might come loose or a solder joint might break (not visible) if they squeezed against each other during insertion. Amongst the cheaper socket risers I had to contend with bent legs when a misalignment occurred during insertion.
Tracking these mis-connections down over 16 chips (times 20 solder points each) was a bit of a (masochistic) game. I've lost count of how many yellow RAM error screens or red Zorro card diagnostic error screens I've seen over the past three days!
Oh, in the first photo you may notice a layer of electrical tape in between each chip and its neighbour JUST IN CASE one of the connections touched another (the chip sockets on the Supra 500XP board abut each other with no room to spare).
Fortunately, all seems to be working now (knock on wood!). The chips are snugly inserted into the Supra 500XP and have passed two cycles of RAM testing (I'm going to run them all afternoon on test mode tomorrow).
Sooo....8MB of 1Mx4 SOJs adapted to DIPs, totally from spare parts lying in my parts stash. I came close to saying this project cost me nothing, but yesterday my de-soldering iron burnt out and I had to buy a new one for $30 - I don't know if I would count that toward the cost. Even so, I'm still a little ahead. A lot of labour though! Was a fun exercise....now I can REST and the family will be shocked to see me again - I've been in my workshop so long!
PS: the pink dots (nail polish) on the chips just indicates to me which way they should be inserted - I was doing things by rote near the end - inserting and removing chips to diagnose problems - and so I was afraid I'd miss the tiny black orientation dimple on the chip if I didn't mark it more obviously.
