How many units have you tested? Is your 82% based off a statistical mean of samplings or a single data point? If you like I can set up an adjustable dummy load and some AC metering to get an accurate sample of in/out efficiency numbers across the load range from a dozen or so random PSUs for a bit of rigor.
I tested several from different sources because I was confused by my initial result and wanted to verify. To be clear I'm not saying that 82% is the gospel but I'm saying that of the several I tested none of them where even close to 90% they were all in the low 80's which is very far from the claimed 90-91. Not only that, but, relative to every other supply I tested these were hands down the absolute worst. No amount of statistical variation can explain that away.
I was basing the efficiency estimation off the 80Plus certification for the model PSU as found here: http://www.plugloadsolutions.com/psu_reports/DELL%20INC_Z750P-00_750W_SO-81_80+_Report.pdf
The indicated form factor is different but the manufacturer, model number and all other specifications are the same so I assume it's the same design/circuitry in a different package, which is not uncommon.
The indicated form factor is different but the manufacturer, model number and all other specifications are the same so I assume it's the same design/circuitry in a different package, which is not uncommon.
Those are clearly _not_ the same supply. The photo alone shows that. Dell reuses model numbers across generations of equipment. Did you do even a cursory test to verify? Seems like a case of ignorance is bliss.
As far as anecdotal evidence goes (and I might ask bobsag3 to confirm this), when Minersource started shifting their hosted units to the Dell Z750P and our boards, they reported a noticeable drop in power consumption over the ATX PSUs they'd been using up to that point (as well as increased reliability). I'd think a large-scale hosting facility would have mentioned sometime in the last six months if their power bill had gone up 10%.
Without knowing the efficiency rating of the supplies they were using saying their power bill went down is meaningless even as anecdotal evidence.
If it's desired that I set up some testing, I'll try to find the time to do so and get some good data for the community rather than relying on the evidence of customer feedback and official documentation. If it turns out that one of the primary selling points for these boards is disingenuous then I guess we have a problem.
I've already decided to go a different route so I don't care what you do but you can't honestly continue to claim those supplies are 90% efficient if you ever believed that to begin with.
With as far off as these supplies are anyone can verify what I'm saying generally by comparing the Z750P to a name brand 80Plus Gold rated PSU using a simple killawatt meter using a miner that draws 300-400 watts as a test load.
ZP750W on both 110 and 220 @ 350W load (1 S3) consumes ~10W less at the wall than my HX850.
