This is kind of embarassing but I made a mistake when assembling my computer.
There's a port on the motherboard labeled pwr_fan. It's a four pin connector.
I accidently connected the power fan intended for a floppy drive, which is also four pins, to that port. An attempted to power on the machine like that, several times (wondering why intermittently it would start up, and every other time, it would not power up, so I figured some kind of grounding problem but apparently, this was the issue).
As a result, it killed my PSU (I'm guessing that's what did it or coincidently my new PSU was bad in addition to this? who knows)
After removing that floppy power connector from the pwr_fan port, the system posted, and once again intermittently it would behave the same.
One thing I did do was (with the PSU switch set to 1 - on) I connected the power cable to the wall and I think that zapped the psu maybe... so maybe I was looking at two problems here. It was a Rosewill PSU and I heard those are faulty to begin with (this after buying one)
After replacing the PSU (with an Antec), the system works fine. It's very fast, and it passed a 24 hour prime95 stress test without issues.
I connected a spare fan to that pwr_fan port and the fan spins, so apparently I didn't damage that port? I did some research on that port and some sources say that pwr_fan port is not for suppying power to a fan but for getting readings from a psu fan... apparently the one on my board powers a fan.
Well, everything works fine and the system runs awesome.
Do you think its still possible I affected the longevity of this motherboard? Because it sounds like what I did was I tried to put power into the board where power comes out of it (not good usually) I'm suprised the motherboard didnt fry. There was no smoking or anything. Just sucks knowing I did this and spent really good money on good parts. I'm very particular.
My only concern is , is this board only going to a few months instead of you know 5 - 7 years, after all this?
Stupid mistake, ugh! lol
FYI my sysem specs are:
i7 950 - Overclocked to 3.7
ASUS Rampage III Gene
6 Gigs of Corsair 1600 RAM
Plextor SSD Sata 3 128 gig drive (6 gbps)
I like this alot better than my e-machines sempron processor machine lol
1) if that spot is not meant to power a fan, remove it. Hook the fan up to the power supply's 4-pin molex. You may need an adapter, if so it should be in the power supply box. Case fans usually have the molex power plug AND a motherboard plug.
2) Your PSU has protection circuitry to prevent it damaging the motherboard. You likely caused a surge in current which fried the protection circuitry killing your PSU. A better PSU might simply reset or blow a fuse.
I'm surprised your PSU died under those settings. I'm not sure I'd use that floppy drive again.
About point 2) I've read some threads on the Internet about others who've connected this floppy power connector to that pwr_fan port on the board accidently, and they've fried the motherboard doing that.
When I connected that spare fan to the port to test out its functionality, I was getting RPM readings on that port and the fan was working. Wierd.
But I guess I'm fortunate to still have a working board after this. Will be sure not to make that mistake ever again.