> What do you think is the sweet spot?
Without seeing an efficiency graph for any given PSU,
you can expect efficiency to peak at or about 50% utilization:
thus, the peak for a 750W PSU is close to 375 Watts;
peak for an 850W PSU is close to 425 Watts.
But, I doubt that the efficiency for either of these PSUs
will fall off too much when the loads exceed 50%.
Here's an interesting comment at Newegg's webpage
for the P183:
http://www.newegg.com/Product/Product.aspx?Item=N82E16811129061&Tpk=N82E16811129061
I purchased the CP-850 power supply that works exclusively with a handful of Antec cases and this thing is amazing. The PSU controls fan speed based on heat generated and the load requirements of your system. It also has an external fan mounted to pull in more air in addition to the air from the intake fan in the front of the case, so the air is pushed and then pulled over my drives. Nice arrangement Antec!!
[end quote]
The comments at Newegg's webpage for the CP-850
are equally interesting, imho:
http://www.newegg.com/Product/Product.aspx?Item=N82E16817371024&Tpk=N82E16817371024
Pros: Is there a better PSU for the money? Outside reviews at Silent PC Review and Hardware Secrets confirm this is a genuine, run-your-sli/xfire-all-day-and-all-night 850w CPU with excellent efficiency, very quiet operation and a five-year warranty. But it costs 50-70% less than comparable ATX power supplies.
Is the CPX format a pro or a con? On the pro side, having a quiet 120mm PWM fan blowing directly across the components is much more efficient than turning the airflow 90 degrees and it allows the CP850 to be incredibly quiet. If building PSU's this way allows Antec to sell them for less (and there has to be some reason for the price difference) that's the biggest pro of all.
The CP850 is a huge pro if you have or are moving to an Antec P183, P193 or 1200 case. Straight up, you'd be a fool to use any other PSU with those cases.
But should the CP850 be a reason to consider those cases over something that only takes an ATX supply? Yeah, I think so. I am that happy with the CP850.
Cons: Sexy the CP850 is not. The fan is not lit with even one LED and Antec made changing it into a needlessly difficult exercise, and the wiring harnesses are only semi-modular.
But the fixed harnesses have what you'd expect any enthusiast to use for a basic build, so the only effect of not having a fully modular harness is that you don't get to click in the harness for your motherboard, video card, SATA drives and Molex leads for the fans.
The fan is, surprisingly, a slightly more serious concern. I don't care about lighted PSU fans, but it's just as difficult to replace the stock Protechnic fan with something like a Noctura or Noiseblocker. Antec aimed the CP850 directly at the silent and low-noise enthusiast community, and it was a big mistake to make fan changes so unnecessarily difficult.
Other Thoughts: The standard line on the CP850 is why did Antec make this PSU when it only fits three cases? I know this is a minority view, but after living with the CP850 for a month, I'm wondering why companies like Silverstone and Corsair are staying with the ancient ATX format for their high-end cases and PSU's?
ATX was created when a bleeding-edge system might require a 200w PSU and having a RAID array in a desktop system was unthinkable. Now any decent gaming system is going to chew up 500 watts and a SLI/X-Fire setup can easily consume 700 watts under load. The result is ATX PSU's have grown longer and traded their 80mm pull-through fans for 120mm bottom-mounted units, but this is trying to cram ten pounds of (ahem) in a five pound bag. CPU and GPU heatsinks have more than doubled in size and effectiveness in the last few years. Why should we expect to triple the actual power going through an ATX PSU and keep it in the same format created twenty years ago?
[end excerpt]
MRFS