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A quick look at Corsair's Professional Series AX1200i digital power supply

A digital PSU with software controls

Your PC's power supply may be the most critical component in the entire system. It's charged with feeding everything from your CPU to your graphics card to your SSD with a steady flow of life-giving electrons. If a power supply goes bad, it can damage other system components in a puff of magic smoke. Even when operating correctly, lousy PSUs can exhibit poor efficiency and high noise levels.

Why don't we cover them more? Frankly, because PSUs are rarely very interesting. They convert AC to DC power and, well, that's about it. The major brands tend to produce solid units, and there are few features to differentiate one from the next.

We may be on the cusp of a revolution of sorts, though. Consumer-grade PSUs have long used analog circuits to covert AC power from a wall socket. At Computex a couple months ago, we caught our first glimpse of Corsair's Professional Series AX1200i, which taps a digital signal processor to accomplish the same task. Switching to a DSP cuts down on the number of components, purportedly improves efficiency and voltage regulation, and enables some very cool software controls. According to Corsair, DSPs are also the wave of the future; all PSUs will have them in a few years' time.

If you believe the hype, the AX1200i is the world's first digitally controlled desktop PSU—and a sign of things to come. We've been playing around with one and its accompanying software for a few days, and the combination is definitely interesting.

The AX1200i is a rather imposing power supply. It's nearly 8" long and features a giant 140-mm fan. The exterior is ribbed, and the fan grill has horizontal bars to match. For something that will spend its life tucked away and out of sight, the AX1200i looks pretty good.

As its model number implies, the PSU is rated for 1200W output—1204.8W, to be exact. Impressively, all that power can flow through the single 12V rail, which supports up to 100.4A. The 3.3V and 5V rails are limited to 30A each and a combined output of 180W.

Corsair claims the DSP in the AX1200i allows the PSU to maintain tight +/- 1.5% tolerances along its main rails. The digital circuit can compensate automatically for dropping voltages, the company says, and it purportedly reduces the amount of AC ripple voltage on each line. According to Corsair, the AX1200i's ripple voltage is less than 30 mV for the 3.3V and 5V lines, and under 40 mV for the 12V rail.

In part because the DSP reduces the total number of components in the circuit, the AX1200i is highly efficient. The PSU has an 80 Plus Platinum rating, which means it maintains an efficiency of 89-92% at loads between 20% and 100% of total capacity. Corsair has also made the PSU very quiet. When the AX1200i is running at less than 30% capacity, a still-generous 360W, the cooling fan stops spinning entirely.

Modular PSUs are fashionable these days, and each and every one of the AX1200i's tentacles can be detached. There's certainly no shortage of connectivity. In addition to one 24-pin and dual 8-pin motherboard connectors, the PSU comes with six 6/8-pin PCIe connectors and a generous handful of SATA and Molex leads.

From this angle, we can just make out the PSU's "self-test" button. Press it, and the AX1200i checks its DC output voltages and fan. This functionality is enabled by the DSP, which lights up a green LED if all is well. Impressively, the diagnostic test is designed to run with the PSU connected to a wall socket and nothing else. It doesn't seem to work when the AX1200i is attached to a system, though.

The last bit of hardware is the Corsair Link interface, which hooks up to a motherboard's internal USB header. This connection isn't required for the PSU to operate, but it is necessary for monitoring and manipulating the PSU with Corsair's software. That's where things get really interesting.