Ok, so I got a new Antec Sonata III case which includes an Antec EarthWatts 500 power suppy.  After installing both, I see that the power supply has both a 4 pin and an 8 pin +12V, and as my Asus P5K-e / WIFI mobo has an 8 pin connector, I thought that I should use it over the 4 pin to possibly increase stability and possibly reduce heat (same amount of power through twice the number of cables should be a good thing, no?).  The computer booted up, and everything went fine for 2 or 3 days.  I then ran some Prime 95 over the weekend (stress testing) to see if this case cooled as good as my last one.  After maybe an hour, I hear my battery backup beeping at me, I go see what's the issue, and the computer has shut down and won't boot back up.  I then take everything out the case, install it all back in my old case with my old power supply (Antec EarthWatts 430 with only a 4 pin +12V connector), and thank goodness everything still works fine!
 
After looking back in my mobo's handbook, I see that it says "Use only either a 4-pin ATX12V or an 8-pin EPS +12V power plug for the EATX12V connector.  I then see that the EarthWatts 500 doesn't have "EPS" on the 8 pin connector.  Did the fact that I used a non-EPS plug cause the power supply to burn up?  Should I have only used the 4-pin like I did with my other power supply (and am still doing now)?
 
Was I dumb to think that 8 would be better and more stable than 4?
 

Anyone?  I'm now seeing that the 8-pin connector might be "EPS".  What's the difference, and why does it matter?  Aren't they all just +12V wires?  
 
If the motherboard really really really needed "EPS" on the 8-pin, why did it work fine for 2 days before I stress tested it?  Then, once the power supply crapped out, everything else was fine (mobo, CPU, memory, GPU).  You would think if it really was an "EPS" issue that it would have been the mobo that was damaged, not the PSU.

What CPU are you using?

Intel E2160 OC'ed to 2.7 (300 fsb x 9).  The board isn't getting OC'ed at all, since it's spec'd to 400.  I was running the RAM at 400, and the GPU isn't being OC'ed at all.  
 
2.7 gHz on that chip is nothing, and should be well within the power supply's capability.  This is especially true since since the "incident" I have gone back to my EarthWatts 430 (a lesser unit), and it's doing fine.  
 
To resolve the issue, newegg is giving me a huge discount on another 430, and I'm going through the RMA process on the 500 directly through Antec.  
 
My question, though, is will it be safe to again use the 8 pin connector on a new EarthWatts 500, or should I simply use the same 4-pin that I've used all along with no issue?  I was just thinking that using 8 pins instead of 4 might help with OC potential, stability, and with heat (or at least it wouldn't hurt).  

    I have never heard of an 8-pin NOT being EPS, EPS means it comes with an 8-pin connector.  The board might have some odd problems with 8-pin connectors, though I can't think why it would make a difference, it is most likely not the CPU connector 4 or 8 pin.  You do not need an 8-pin for a dualcore CPU, but its nice to have that extra juice so it is one less thing to think about when considering upgrading.  Honestly though whether you used a 4-pin or and an 8-pin, if the problem WAS the PSU then it just died out of just being defective.  I would definately try the 8-pin the next time around, if it happens again then I believe your motherboard is drawing too much energy, or some other component is doing it.  Just my opinion, hope it helps.

The 8-pin PCIe connector is keyed differently than the EPS 12V connector, so it should have been impossible to mix those when connecting your equipment (that was my first thought when reading the OP).  
 
My brother had a similar problem, but we ended up concluding something was shorting his motherboard (the sound deadening material on the MB mounting tray).  Try booting it up as an open-bench layout not inside the case (simliar to what you see in computer component reviews online).  Luckily for you Antec is based in the US and has excellent customer service.

I'd hate to kill 2 of these EarthWatts PSU's!!  I mean, if it was working fine with only 4 pins, I might as well just continue.  Anyway, why I don't think that the power supply is "EPS" is because if you do a search on newegg, go to power supplies, narrow the search to only Antec (EarthWatts 500 is in the list), but when you narrow again to EPS "enabled ones", the unit is no longer there.  
 
It does have an 8 pin connector, and it was powering my computer for a few days before stress testing.  I'm just glad that I get to RMA the PSU unit alone (and not it with the case that it came in) back to Antec directly for a replacement.  Newegg wanted me to ship the PSU and the case it came in back to them ($30+ in shipping)!!
 
As of now, my EA430 is doing the trick quite nicely with it's 4 pin connector.  Can someone else confirm that it will be ok to again use an 8 pin from the above power supply in an Asus P5K-e WIFI?!?!?

 
The power supply in question has 2 6-pin PCIe connectors.  Neither were used in the 8-pin CPU socket.  As I said, it was fine for a few days, then died during stress testing.  
 
What is "EPS", and how does that really differ from just two 4-pin CPU power connectors side by side?  Can anyone confirm or deny that the power supply in question has EPS?  One review I saw said that it does indeed have it, but neither antec or newegg  lists it on their specs.
 
Does using 8 pins over 4 really help or hurt anything?

Look here:
http://www.xtremesystems.org/forum [...] p?t=108088
The earthwatts is not even listed.
Get a tier 3 PSU or better.

bobbknight, the EarthWatts is a Seasonic-produced unit.
 
If you'd read jonnyguru's review of an EarthWatts 500, you'd know that they're quality units.
http://www.jonnyguru.com/modules.p [...] ry&reid=35

There are other guides out there, but this one discusses the EPS connector: http://www.playtool.com/pages/psuc [...] ctors.html
 
About 3/4 of the way down the page, there's a discussion about voltages, power, and the EPS connector that should help you out.

Use the 4 Pin.  You only need the 8 pin if you are using a Pentium extreme ( 130 or greater Watts)  your no where near that point.
Refernce my mother board book and previous threads on 4 pin vs 8 pin requirements.
 
The connections on the socket (+12V pins are shorted and Gnd pins are shorted); so only difference is 8 pin has decreased contact resistance and decreased wire resistance.  I had 4 pin installed, chanced PSU and used 8 pin - to lazy to swap back.  Even at 100 Watts, a good PSU 4 pin would handle the Current with negaible IR drop
 
I strongly fell that you got a defective PSU.

My P5K-e/wifi-AP came with a cover over half the pins on the CPU power connector, is this because you shouldn't use them?
 
*shrug*

Nope, just checked the manual
 
"Make sure to remove the cap on the EATX12V connector before connecting an 8-pin EPS +12V power plug."
 
Don't know then chap, sounds like just a bad PSU.

Right, I read the manual as well.  What I'm unsure of is if the 8-pin that I used was an "EPS +12V plug".  It was 8-pin, that's for sure.
 
If I'm ok in just using the 4-pin, will that still be true if I upgrade to a 45nm quad core, and OC it to 3.5+ gHz?  Again, this will either be with an EarthWatts 430 or an EarthWatts 500.  

As the old saying goes - If it walks like a duck and it quacks like a duck, it will propably taste like a duck.
 
(1)  Look at the pin-out for the connector, and the pin-out for the PSU plug.  DO they match.
 
(2)  Does the Plug properlt fit the conector (was going to say does the male fit the female without forcing - Didn't sound right)
 
(3)  If multi-rail, Is there sufficient current capibilities on that rail.
 
If the answer to all 3 is Yes - Then mate it.
 
Again, as far as 4 vs 8 pin - Is the Current required by the processor (OC or stock) above the 120/130 watts.  Even if not there should be no problem using the 8 pin configuration if the above 3 pointers are verified.  EPS Who?

Your problem might ly in battery backups as well. You might have too much running through one section of the backup, like the battery side. Mine did that once and shut everything down. I unplugged and moved my color laser to the surge side and problem solved. I'm not saying that PSU is not blown but that fact the backups was beeping means power was cut there not the computer. Your backup normally doesn't beep when you shut down your computer.

 
Yeah, that was also my concern.  Now, the PSU is shot, as I moved it to another computer I'm working on, and it wouldn't light up the LED on the mobo like the puny old 250W one I had plugged in there did.  It's being RMAed back to the manufacturer, Antec, for a new model.  When I started hearing the beeping from the battery backup, I knew something was wrong.  I hit the reset button on it to stop the beeping, and then tried to turn the computer back on, and nothing.  I only got it back up and running (again through the battery backup) when I switched case and PSU.  
 
As for the previous poster, the male and female ends were keyed perfectly, so I mated them (that didn't sound right either).  It is in fact an 8 pin.  How do I know how much my current (or any future) CPU is drawing/needing?