Alecthar

I thought the same for PSU construction that a standard spec is used to build and should just "work" and Seasonic is supposed to be the undisputed "best". I would be inclined to think it was the MB if I had not tried a corsair from buddies willing to help trouble shoot and they worked as expected. I still have one in my rig as my friend is waiting for a replacement video card. Seasonic has contacted me and stated they are sending me an X760 today as a replacement. Hopefully that will be the end of it. Calling Seasonic the undisputed best would be overselling it, probably vastly so, but they do make a lot of very nice supplies. What kind of Corsair unit did you test? Many Corsair units are internally identical to certain Seasonic counterparts, so it's more than a little likely that you used a Seasonic-built supply to troubleshoot. Given that both of your Seasonic supplies exhibited different undesirable behaviors, it's certainly possible you got a pair of bum supplies.

I've honestly never heard of an "incompatible PSU". All PSUs use standardized sets of pins and cabling. The internals may differ, but one quality PSU should behave much the same as any other, as far as startup procedure goes. The motherboard actually handles the signaling of the PSU to send power. If the system is actually booting up rather than just fans spinning up and the like, with no system activity occuring, then the likely culprit is your motherboard. Sending power to the motherboard wouldn't cause the system to start up, even if the PSU were "sticking" on and still sending power, the most it would do is power components that don't rely on information from the motherboard to startup (fans, water cooling equipment or the like). My assumption is that there's a power-related function on the SuperMicro boards that's designed to signal server PSUs, but for some reason is triggering something unique in the X series PSUs that causes the issues, maybe the PWM circuitry that manages the fan (it's different from most other PSUs). Seasonic is a sterling PSU maker, though. You shouldn't let this issue dissuade you from purchasing their supplies in the future. This is literally the only time I've ever heard of something like this.

Assuming you're running all green drives, that's probably more power than you need, but there's nothing wrong with it.

Your math is incorrect. You don't figure out total +12V wattage on a multi-rail PSU by taking the rail amperages, multiplying them by the voltage in question and adding them together. The PSU label will have information for the total combined wattage. Basically the reason for this is that a multi-rail PSU is really just a single rail PSU with the current split up for OCP, so just like a single rail PSU it can only pull so much wattage. Each rail can go up to a certain maximum current before tripping OCP, but the supply as a whole cannot sustain all of the rails running at their maximum OCP rating. And PeterB is absolutely correct, after ATX 2.3, there is no absolute over current limit. I do wish someone would make a more server friendly consumer PSU. Having molex/hard drive power spread out over multiple rails would be nice. I mean, sure single rail makes things easy in the sense that you know there's no chance of tripping the OCP without just plain overloading the supply, but if you get a short and you're running a, say, 750W PSU, something is going to fry, and I wouldn't put my money on "not the drives".

Just wanted to mention the upcoming NZXT Source 210. It's supposed to be very affordable (~$40) and with 3 5.25'' bays and 8 3.5'' internal bays you can run a single 5 in 3 cage and hit 13 drives for significantly less than the cost of running a 15-bay tower build. It's also very slick in terms of aesthetics.

Both of the supplies you reference are from Corsair's TX line, the difference is that the first one is an older version of the unit, it's less efficient and performs worse. It's still a very solid supply, but the TX750 V2 (the second one you linked) is a much better buy overall. My feeling is that any price premium on the older unit is likely due to declining supply.

I just wanted to toss in here that the Antec High Current Gamer PSUs in the 400W-620W range are based on the very solid Seasonic S12 Bronze platform. These are a slight efficiency upgrade over the standard S12 (also Antec Neo Eco from 400W-620W). Internally they are unchanged, and often come at a significant discount vs. their Seasonic branded counterparts. For example, the Seasonic 520W S12 Bronze is currently $80, whereas the Antec HCG 520W is $60.

Well, the Antec Neo Eco's are less efficient than more recent PSUs, one of the reasons Seasonic doesn't actually retail those standard S12s anymore (you can get S12 Bronze supplies, though), but they're relatively inexpensive and very reliable. The TX's, new or old, are both very solid supplies, and good values. If you consider the rebate (I don't usually, but that's just me) the older TX line is probably a better value, but if you don't count on getting that money back, the TX V2s are better units all around, and really nice values, as are the virtually identical XFX Core Edition 650W units.

You'd be incorrect. The old TX series were a mix of Seasonic and CWT based units, while the TX V2s are based on the same Seasonic platform as some of the XFX Core Edition units. Also, if I recall correctly the Antec Neo Eco units are based on Seasonic S12 platform.