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.
Corsair Link compatibility
The latest version of the Corsair Link Desktop software incorporates a new Power tab that pulls data from the AX1200i. There are monitoring windows for the three main voltage rails in addition to separate displays for the 24-pin connector’s 12V line and the AC voltage at the wall socket. The individual current trackers for the auxiliary PCIe power connectors are particularly nice.
Next to each one of those PCIe monitoring windows is a slider that can be used to set an arbitrary over-current point from 20-40A. This options allows users, effectively, to roll their own multi-rail configs, and changes can be made in real time. The app also supports multiple profiles for folks who want to save different setups.
Up top sit two graphs that monitor the PSU’s input and output wattage, plus a calculated efficiency based on the difference between those values. The power-in numbers were within a couple watts of the reading on our Watts Up power meter.
Obsessive fan-control nerds (like yours truly) will be pleased to note that the PSU’s solitary spinner can be toggled between a “quiet,” temperature-based speed control profile a static, manually-tuned percentage of full speed that can be set no lower than 40%. In quiet mode, I don’t believe our Sandy Bridge-E test system, which is equipped with a Core i7-3960X and a hot-clocked Radeon HD 7970, ever drew enough power to spin up the fan.
The AX1200i reports its own temperature to the software, of course, and users can set email notifications associated with specific temperatures and fan speeds. Those triggers can also be set to run files, to spin up system fans, and to activate the LED light strips that come with Corsair’s standalone Corsair Link hardware.
True to the software’s mission as a system-wide monitoring and control application, the AX1200i “fan” and “temp” variables can be renamed and assigned to different groups. You’ll need other Link-compatible Corsair gear to really take advantage of the software, though.
Corsair has done a good job with the user interface, which can be switched between a couple of different skins and loads of font colors. Users have some freedom in how the panes are arranged. They can also control whether select panes are pinned to the UI, pop over it when activated, or float freely the desktop. Logging is built into the app, although the only PSU variables available are the AX1200i’s temperature and fan speed. It would be nice if Corsair enabled logging for the individual voltages, amperages, and wattages that are already displayed by the software.
We’ve been too busy with other projects to put the AX1200i through its paces on our custom load generator. To reach any meaningful conclusions about performance, we’d really need to pit Corsair’s new hotness against a couple of its high-wattage rivals. We may do just that, but for now, we’ll simply note that we’ve had very good experiences with other models in the Professional Series lineup. Although none of them have the AX1200i’s new DSP, we have multiple models and units deployed in multiple labs, and we’ve yet to have a problem with any of them.
New innovations tend to trickle from the top down, and the AX1200i is definitely a high-end PSU. Retailers are expected to charge $350 for the thing, a $50 premium over the existing Professional Series AX1200. That model is only certified 80 Plus Gold and lacks the DSP-enabled Corsair Link compatibility. Both are covered by a seven-year warranty, though. If we were putting together the sort of ultra-high-end system that demands a 1200W PSU, we’d be inclined to pay the extra for the AX1200i.
Based on our limited time with the unit, the AX1200i seems like a solid power supply. What’s exciting is the software monitoring and control enabled by its DSP. Enthusiasts have always liked tweaking their setups and keeping an eye on what’s going on in their systems. Now, Corsair is giving us a glimpse inside the power supply. If this is truly the direction for future PSUs, we might need to start paying more attention to them.