Antec CP-850: Unique PSU with Top Performance

August 29, 2009 by Mike Chin

Product	CP-850 850W Power Supply
Manufacturer	Antec
Market Price	~US$125

The CP-850 was first shown by Antec to tech journalists all the way back at CES in the start of the year, then released to market in February. This power supply model is very unusual in that it has a form factor — CPX — which makes it compatible only with a handful of cases, namely the Twelve Hundred, P183 and P193 cases made by Antec. Partly because of its narrow target market, the CP-850 has not been quite as popular as it might have been with a more universal form factor.

It's not as if Antec is lacking for power supplies. The brand has no fewer than eight different categories of PSUs for a total of some 29 different models. Several of these lines are quite powerful or high end; for example, the impressive flagship Signature series, TruePower Quattro, and the model on hand, the CP-850W. Exactly what Antec hopes to achieve with such a vast lineup of mostly ATX power supplies is a bit puzzling. Perhaps it's a strategy of domination by SKU blanketing.

The CP-850 is another collborative result between Antec and Delta Electronics, a relationship that already produced the excellent Signature series PSUs. The CP-850 is unique enough, not only among Antec power supplies but among PSUs in general, that some examination of the marketing and technical blurbs are useful. Let go directly to the key features which sets this power supply apart. From Antec's press release and marketing sheet:

"The CP-850's new "CPX" expanded form factor allows for better circuit board layout, more room between components for airflow, and a straight-through air path that takes full advantage of the large 120mm Pulse Width Modulation (PWM) fan. The CPX form factor is thus able to provide quieter, cooler operation in addition to the CP-850's preferred price-to-performance ratio... By breaking the mold of standardized power supply size restrictions, the CP-850 design is able to provide an excellent price-to-performance ratio. A silent rear 120mm PWM fan and dual PCB layout also ensure optimal cooling performance and reliability"

The use of a 120mm fan is no big deal; they've been around for years now, and even been exceeded in size by 135mm diameter fans. What is unique about the CP-850 is use of the fan not in a bottom position where the forced airflow must turn 90 degrees before it can exit the power supply, but placement on the back panel. It's a fan position that allows air to flow straight through the PSU in any computer case. The design has many physical ramifications, the most important of which is that the PSU must be tall enough to fit a 120mm fan on the back, which makes it substantially taller than a standard ATX12V power supply, and it cannot be installed in the vast majority of cases on the market today. The aformentioned large cases — Twelve Hundred, P183 and P193 — were designed or modified specifically to be compatible with the CP-850. Alas, no other cases need apply for partnership with the CP-850. The other highlighted snippet about dual printed circuit board layout isn't clear right away, but it becomes evident when the unit is opened up.

Our technical contact at Antec mentioned several aspects of the CP-850 design long before the sample arrived. Fundamentally, the straight-through airflow with the big fan and the dual PCBs keeps all the core heat-generating components in the center of a bigger casing; the lower thermal/power density has many benefits for reliability, cooling and cost:

• Not only can components be kept cooler with lower fan rpm, but they don't have to be rated for as high temperature, and still be extremely reliable and long lived. Lower temperature rated components means lower cost.
• More room in the casing means the option to use larger parts, which again are less costly than smaller power electronic parts of the same rating.

These engineering efficiencies allow very high power capability and performance at modest cost. This is a good thing: Without the attraction of lower price, a PSU with a form factor that can only be used with three cases is unlikely to be seriously considered by most buyers. A search on the SPCR Shopping Engine as of late August 2009 shows the CP-850 to be available for as low as US$115, which is a real bargain among premier PSU brands of similar power rating. (Antec's own Signature 850 comes in at $215 and Seasonic M12D-850 at $180.)

The photo on the retail box tells the story of the fan. Nicely packed in closed cell foam with detachable output and AC cables, and a paper user guide. It's modular and comes with many detachable output cables, but many cables are permanently attached.