So, good news. Really,
really weird good news.
I figured out what was preventing the computer from booting.
It wasn't the mainboard.
It wasn't the processor.
It wasn't the RAM.
It probably wasn't even the power supply, though it was time to chuck my PSU if the multimeter readings were assumed to be accurate.
So what was the single item that had me spending hours testing, reading countless forum posts, and (figuratively) tearing my hair out?
It was
the backplate for the heatsink.
Yes, that's right, the backplate for the heatsink was preventing the computer from booting. I know it sounds crazy--I couldn't believe it at first myself--but I tested, re-tested, and re-re-tested to confirm.
A few pages back, I mentioned that I was trying to pin down which heatsink/fan to purchase from Newegg. I finally decided on the
MASSCOOL 8W553B1M3 90mm Ball CPU Cooler, in part because I wouldn't have to deal with those infernal Intel push pins. (Those pins are the bane of nearly every system builder's existence.) The heatsink/fan was super-easy to install and the fit was perfect, so I didn't think of it again, even while suspecting several other components, until today.
That's when--after I had already packed up the new 450W PSU I bought to return it after church tomorrow--I thought I'd remove the heatsink, put a dab of thermal paste on the CPU, and boot the system for about 10 seconds to see if the CPU heats up. (I was trying to gather data to decide whether the CPU might still be good or not.)
So, yes, I broke the cardinal rule of system building: Never, ever,
ever boot the system without the heatsink attached to the CPU. This is dark arts kind of stuff here.
But imagine my surprise when, after pulling the heatsink/fan and heatsink backplate, connecting the power cable to the power supply, and shorting the power button jumpers with a screwdriver (yes, I actually did that), a few seconds passed and I heard the BWONG of a CRT monitor turning on.
Pretty awesome moment, I have to say.
So I shut the system down for fear of frying the CPU, reattached the heatsink backplate, and booted the system again. Nada.
Removed the heatsink backplate. Booted just fine.
Reattached heatsink backplate. No boot.
I then placed the heatsink/fan on top of the CPU and turned the system on. And it booted.
So it's definitely the heatsink backplate.
Given the bizarre results of testing, I can't help but think of Sherlock Holmes: "When you have eliminated the impossible, whatever remains, however improbable, must be the truth."
So my plan now is to buy a 600W power supply and new heatsink/fan--one WITHOUT a backplate--from Newegg and see if I can tap some secret well of patience while I wait for the items to ship and arrive.