Hi all. This is my first post in this forum.

My motherboard is a Gigabyte GA-586HX with a Pentium MMX 200 MHz and 352 MB of RAM running Win98SE.

On this board there is an empty socket designed to receive what's called a TAG RAM in the manual (U4 chip). This chip sets L2 cache cacheable size to 512 MB (64 MB without). The specs call for a 16Kx8-15 chip. I ordered one from eBay.

Now for the bizarre part. The computer will boot only if it has been off for many hours. It seems to work fine when it boots (tests with SiSoftware Sandra show a definitive gain in cache speed when the chip is in place). As soon as I try to reboot, nothing happens. This is true even if the reboot is called immediately after a successful boot. A POST diagnostic card doesn't show any code when the boot fails. When the chip is removed, everything returns to normal.

I stripped all the cards except for the video; no luck.

I guessed the problem must be electrical. With this in mind, I checked the only non-SMD components near the chip (I can do this because their pins are accessible from the back of the board, thanks to an opening in the case). Those are a voltage regulator (AS2830AU) and an electrolytic capacitor of unknown value (I can't see the value because of its position inside the case, and I don't want to remove the board from it, which is a pain). I tried to determine the value of the capacitor (with the computer turned off), but the results are inconclusive; one instrument gives me around 980 uF and the other 0. The voltage regulator gives 2.15 V on the Adjust pin, 3.41 V on the VOut pin, and 4.86 V on the VIn pin. This is as far as I can go since I don't have the board's schematic and my electronics skills are limited.

Any insight would be appreciated.