rasz_pl wrote on 2026-10-27, 02:57:

I saw that, same corner as the bend pin at the start of the thread, might have been ripped before you desoldered the chip. You can try gluing them to pcb if you have soldermask or a high (very) temp glue.

I'm not sure if I did it or not; although I tend to think that they were already loose. When something doesn't work, I usually put a head-mounted magnifier on and have a close visual check before getting the meters out. I saw that the corner pins had been crushed, and tried to separate them gently. While doing that, I noticed that one of the pins was actually no longer connected to its trace. It was when I tried to solder it back down that I could see that a few of the traces were loose because they were moving about as I was trying to solder them. I do have solder mask, but I'll probably leave that until after I have soldered my replacement IC in position. For now, I just want to disturb them as little as possible.

Well, I finally got my M1487. It went in okay, but I wouldn't want to have to do it too often 😀 Anyway, I think I have a reasonable reset signal now. It goes high for a fraction of a second, then comes low, which is what I think it's supposed to do, to give everything a chance to settle down. It still doesn't work, though, so I checked a few other things. I have a resistance of only 3 ohms between ground and all the 5V lines at the power connector. That seems rather low to me, so I'll probably have to check some nearby tants. Oddly, I do get 3.45V at the CPU VCC (I have an IBM 486 DX2-V266GA and an IBM 486 DX2-V366GB, and I think the 'V' means they want 3.45V, and that agrees with the ABit manual); and I also get a good clock at the CPU, too. So that 3 ohms isn't breaking everything.

> 3 ohms between ground and all the 5V lines

8 watts of power, something is getting really hot now. Coincidentally thats about as much power as 3.3V 486 would use, but unpowered LDO would not pull any power and definitely not read as 3 ohms.

so now proper reset goes to both ISA and CPU? back to Re: Trying to resurrect an old 486 motherboard. checking if CPU tries to fetch any data

It seems to be those cache RAMs, which do get very hot. Each has a resistance of 11 ohms between VDD and VSS. I'll check ISA and busses tomorrow.

wasnt cache backwards when you started? those are all fried now

No. Someone suggested it might have been; but the notches have always been correctly aligned while I've had it. Maybe in the past, though?