So here goes the sad story (maybe I'm stupid and did something totally wrong, but I wasn't aware of that):

Some time ago I bought an IBM 5x86c chip in QFP package, soldered onto PCB originally used in Thinkpad laptops (i got that one before I knew that). Quickly it turned out that it won't fit into my mainboard's socket, because a) it extends beyond it and b) it has some additional pins. So I decided to buy some SIP pin headers and just installed them on the CPU pins. Now I was able to put it into the socket, but it turned out that some soldering needs to be done to make it work. I soldered some cables and then it started to work.

But there was a problem: those extended pins were designed to be soldered onto PCB and not to be used in a socket. So they were a bit too thick, a bit too short, and nickel plated, maybe with addition of tin. It worked, but I was afraid that long-term usage of such CPU could damage the socket: it caused significant friction and also the contact between gold and tin or nickel could cause corrosion after some time. So I took that CPU out and didn't use it for several months.

Recently an idea came to my mind that I could solder gold pins onto those pins I already put on the CPU and everything will be perfect. So, I bought some SIS pin headers and a universal, drilled PCB board. I did some milling in order to make the holes wider and started soldering gold pins - one row at time. It started to look like a 486 voltage converter board now, only without any electronics.

I did that everything with the CPU attached to the board, because it had all those extra wires soldered and I didn't want to unsolder them. After the soldering was done, I checked if the cpu will work...
and it didn't. I decided to cut the wires and take out the CPU. Then I cut away the extra row of pins it had so it would fit into 4DPS mainboard I got recently (before that I used it with Abit PB4 and there was no way to fit it into socket without extending pins) and soldered new wires to make it compatible with regular socket. It still doesn't work...

I decided to check if there were any problems with the extender itself, but it actually worked perfectly with another 486 CPU. I removed the remaining cables and, well, i won't find too much use for that thing now but at least it works and the socket and golden pins got recycled.

Well, it is clear that I made some mistakes here, if only I had soldered those extra wires to the CPU itself at the beginning then I could make that pin extender without involving the CPU itself.

But, anyway, why did it die? It didn't get any excessive heat as it lays ontop of the PCB... could it be caused by the damage of CPU itself (ESD?...) or maybe the CPU still lives and the PCB was mechanically damaged, because of thermal expansion or stress it experienced while fitting the new pins?

I'm pretty sad, it was the only such powerful CPU I had for socket 3... I have to look for something new but these are pretty expensive and rare now... I didn't have a chance to use it too much, but actually that unit wasn't even originally meant to be used in a desktop PC, and modifying it always involves some risk.