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

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 PSUโ€”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 outputโ€”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.

Comments closed
    • rrr
    • 7 years ago

    Ehhh, quick look? Other sites did full reviews, including proper one from likes of JonnyGURU or TPU. How about taking a look into Beast’s anomalies which may be causing some of the odd results it had (like absurd low load efficiencies)?

      • Airmantharp
      • 7 years ago

      Might want to make your criticism a little more constructive. You are getting this information for free after all!

        • rrr
        • 7 years ago

        What’s so unconstructive about it? That I don’t know how Beast operates and cannot provide specifics? How about you try to set example?

    • Bensam123
    • 7 years ago

    Definitely going to give Corsair props for this. This is something that should’ve been done in PSUs for the last decade or so. I guess it shows you how slow parts of the industry move when there is relatively little incentive to do so. More so then that this is coming from one of the newer PSU makers.

    It really is neat that you can manually adjust the voltage rails, but IMO the PSU should do automatic load distribution based on the current loads or trends.

    They should also consider adding a windows gadget for this. I could see this as something I would like to see all the time (probably that way for anyone that’s geeky), but overall most people wouldn’t want such a big program open all the time

      • Airmantharp
      • 7 years ago

      I love the idea- it’s the application that I’m having trouble with. Essentially, who cares?

      Also, more moving parts, more points of failure. The only thing that this PSU appears to set itself apart with is efficiency.

        • DeadOfKnight
        • 7 years ago

        It has the best regulation and lowest ripple ever seen in a PSU. The corsair link and software seems rather gimmicky though. I bet they could save us a bit of cash if they tossed that part out. 1200W is overkill for almost everybody, but you know they want to scalp early adopters as much as possible before releasing cheaper models.

          • Airmantharp
          • 7 years ago

          Well, 1200W isn’t really overkill if you use it- i.e., put three top-end cards that actually need >225W each in a system under load, with an overclocked CPU (or two!), and associated peripherals.

          In the situation that it is needed having the most stable and efficient unit is absolutely worth paying for, I think we can all agree.

          But monitoring software? Nice, but still gimmicky. It’s not like you’re actually going to need to make changes, so you’re really just getting a ‘feel good’. Many would rather it just be $50-$75 cheaper and still have the most awesome PSU money can buy.

        • Bensam123
        • 7 years ago

        I care, tons of hardware geeks do… I think there is a market for it.

          • Airmantharp
          • 7 years ago

          Oh I mean it when I say I love the idea. But with DOK above, why add all of the other crap in- just make a friggen awesome PSU and be done.

          Still, getting a Corsair link HSF and PSU, and whatever else they add all in one system sounds cool, but only in the event that I really actually needed to monitor all of that crap.

    • albundy
    • 7 years ago

    is it professional for server grade? or am I unprofessional in asking?

      • pedro
      • 7 years ago

      Where’s Krogoth when you need him?

      • Airmantharp
      • 7 years ago

      Absolutely not. Professional/server grade is nowhere near this level of quality.

    • Sargent Duck
    • 7 years ago

    This, except at 550 watts with a big ‘ol shiny passive heatsink on it.

    • mako
    • 7 years ago

    I recall reading somewhere that this PSU physically has a single 12V rail. So what’s the benefit of setting up “virtual rails”?

      • HisDivineOrder
      • 7 years ago

      More bullets. For your list. Of reasons to buy the PSU.

      • Airmantharp
      • 7 years ago

      Along with HDO’s explanation (+1), ‘virtual rails’ seems to be an extrapolation of the efficiency and flexibility of using a DSP to control the power plane.

      • cynan
      • 7 years ago

      I wonder if resellers even know the specs of the products they are selling sometimes.

      Case in point. XFX blatantly markets their XFX Pro Black editions (same as Seasonic X series) as being single rail designs. Jonny Guru reviewed one and, after disassembly (as they are want to do) discovered that the PSUs were actually a [url=http://www.jonnyguru.com/modules.php?name=NDReviews&op=Story5&reid=273<]quad rail[/url<] design (see points under "The Mediocre"). Still a great PSU (I have the 1050W version).

    • DeadOfKnight
    • 7 years ago

    Oooo, shiny. Though personally I think I’d wait for an 850W.

      • Airmantharp
      • 7 years ago

      Or 650W. 850W would be a triple GPU system; this thing makes me think of a dual-socket triple GPU system with water-cooling.

        • DeadOfKnight
        • 7 years ago

        Yeah but the cost savings of going from 850W to 650W isn’t as significant as from 1200W to 850W in their existing offerings. Additionally, you’ll probably get to have it operating silently a lot more than with 650W if they turn down the fan at the same load %. A lot of gamers run dual GPUs and overclock them as well as the CPU so the additional headroom would be welcome. It should also benefit efficiency under load. Not that 650W isn’t enough, it certainly is.

          • Airmantharp
          • 7 years ago

          Yup; well, 650W is actually overkill for that too. You want your system to run between 20%-80% PSU output, and I could barely get my system to 75% with both HD6950’s in, 2500k at 4.8GHz and healthy voltage, and both Prime95 and Furmark loading it all up. Real gaming was below 450W at best, so even with PSU deterioration, the system would be good for >5 years.

          I guess I’m just a fan of buying quality lower-wattage PSUs rather than just chasing numbers (not implying that you are!). But I really haven’t seen a ‘rational’ build that needed more than 650W.

            • DeadOfKnight
            • 7 years ago

            You may be right; I honestly haven’t used a calculator to figure out what I need nor have I tested how much I actually use. My 650W never had a problem with SLI except for the fact that I had to use molex adapters for the second card, which is less than ideal. I would definitely go up to the 750W or 850W if that were the case here.

            But I still think there is some value to having your PSU’s fan only kick in during those intense gaming sessions. That said, we don’t know quite yet what wattage would strike that sweet spot if going for this line of products, but I have no doubt they’ll be trickling this concept down later on. By the time they launch a 650W they might have next gen CPUs and GPUs that sip power less too; or a lot more while overclocked and gaming, for that matter. We shall see.

            Edit #13: They should add a preview feature for comments.

            • Airmantharp
            • 7 years ago

            Kill-a-watts are on the shelf at Lowe’s and Home Depot :).

            • DeadOfKnight
            • 7 years ago

            I was still editing my comment and then I reloaded the page and saw that you had already responded. I’m so picky about grammar and breaking up walls of text. I saw some more conjunction errors as well, but I’m done looking at it.

    • Madman
    • 7 years ago

    No spinning fans at 360W?! I want one, NOW!!!

    Then again it probably costs 5k$… ๐Ÿ™

      • Waco
      • 7 years ago

      Reading is fundamental. $350.

      Also – the software makes me laugh. 100% efficiency? I saw it in the pictures here and in the original unveiling. They’re gonna need to work a little harder on the math for that if they want anyone to take that measurement seriously.

      • flip-mode
      • 7 years ago

      Seasonic X series will do that for $125.

        • Bauxite
        • 7 years ago

        Yeah I like my 460, but it does assume some “natural” case airflow if you’re not idling.

        • Airmantharp
        • 7 years ago

        Yup, I love my 650 Gold! Even bought it used off of an [H]’er, it’s a real piece of work

        • cynan
        • 7 years ago

        Or just go with the XFX versions which are usually slightly cheaper.

        Speaking of, I wish TR would include the name of the OEM manufacturer in PSU reviews.

        Edit: According to the JonnyGuru review, it’s Flextronics

      • pedro
      • 7 years ago

      I want to know what impact this has on case airflow.

        • DeadOfKnight
        • 7 years ago

        I don’t think it would really change much for bottom PSU mounted cases that pull in air from outside, but for top-mounting it could change quite a lot. Since the fan pulls air into the PSU and out the back of the case, there would be more positive pressure if it were to turn off. In fact, that would actually work out quite well to keep the airflow through the PSU since it is an escape route, assuming you don’t have negative pressure in your case normally (which you don’t want if you want to avoid dust).

          • Airmantharp
          • 7 years ago

          Right!

          A good bottom mount solution (or any good PSU mount solution) has the PSU pulling outside air in through a filter.

          If it’s pulling air from inside the enclosure, it could make a small difference, but as DoK said, you’re going to want a positive airflow system anyway to avoid dust, so air would still be flowing through the PSU, and the subtraction of some exhaust flow will only increase the cooling effectiveness of other exhausting systems, like blower-style GPU coolers and integrated water-coolers for CPUs.

    • Chrispy_
    • 7 years ago

    [quote<]PSUs are rarely very interesting.[/quote<] Right on the money ๐Ÿ™‚ I can't help but think the market segment for this must be absolutely tiny; By the time you need this much power with this much monitoring, I would imagine the ATX form factor is way out of its league and you should be looking at dedicated rackmount hardware or a blade cabinet. Mind you, the epeen crowd will probably need a change of pants when they see this!

      • Madman
      • 7 years ago

      Spare power != used power.

      • Waco
      • 7 years ago

      I have a 950 watt PSU and my last setup could easily draw a kilowatt from the wall. The need exists, sometimes.

      Personally I’d like to see the same stuff in a ~500 watt PSU.

        • Madman
        • 7 years ago

        The pretty numbers on GPU boxes doesn’t sum up. They are there to make sure you buy a PSU with extra spare power, and therefore don’t run into power fluctuations at higher load levels. Component’s don’t draw that much power in reality from what I have seen.

          • Chrispy_
          • 7 years ago

          You need to check who you’re replying to. Waco’s kit cares not for silly numbers printed on silly boxes.

            • Waco
            • 7 years ago

            This. I measured it with a Kill-a-watt meter. ๐Ÿ˜›

            The current incarnation is more efficient, thankfully. I don’t think I’ve seen over 500 watts loaded except under stress testing.

            • Airmantharp
            • 7 years ago

            Hell, I had to try real hard to make my system with two HD6950’s draw 550W at the wall on a Kill-a-watt, and with marginal efficiency considered, I was still only drawing 500W of a 650W Seasonic X.

            I think I’d be good for a pair of GTX690’s, if I could afford them!

            • cynan
            • 7 years ago

            Having current headroom is essential for overclocking enthusiasts. Using a Kill-a-Watt, my system’s load peak power draw was a good 100W higher when overclocking a single HD 7970 alone compared to stock (around 500-550W vs ~400W). Add in a a second GPU and heavily overclocked quad or more core (Sandy Bridge E) CPU and I could see how you’d be hitting around 900W at peak load. You’d probably need to throw in a 3rd overclocked high end GPU to get to 1200W though.

            As for the digital link, I can see how it might be useful if troubleshooting system instability (essentially if the PSU is working properly), however, you’d expect a premium high end PSU to work well in any case. Overall, it’s just a gimmick.

        • Chrispy_
        • 7 years ago

        Sure, and that’s why I said the market must be tiny.

        I look at your PC and see some pretty high end kit being pushed pretty far beyond what it was rated for. “Enthusiast gaming PC” is a pretty small market already, but if you look at the top 1% of “enthusiast gaming PC’s” from a survey, I would be confident that your PC would still be in the top 1% of that elite sample.

        I think the most power I ever drew from the wall (well, UPS with digital readout actually) was 850W from a [i<]pair of overclocked Opteron 2350's[/i<] and a [i<]pair of 4870 X2's[/i<] . It was a work experiment with parts that weren't together as a permanent solution in order to benchmark rendering software on in-house projects. It resulted in our first A64 CPU-only renderfarm but it also highlighted to me just how tiny a market segment the 1KW+ power supplies occupy. Since that day, things have become less power hungy, not more. The notable exception being graphics cards, though those 4870's would probably give the GTX480's and 690's a good run for their money in the power draw stakes.

          • Waco
          • 7 years ago

          Agreed. My dual 4870X2 / Phenom II setup was my most power hungry.

          Moving to an i7 and a 5970 actually dropped my power consumption by nearly 50%. I could save a lot more if I didn’t OC my 5970…but what’s the fun in that? ๐Ÿ˜€

          You really only need crazy PSUs today for multiple top-end GPUs, overclocked, along with a power hungry CPU. Even then I find myself hard-pressed to configure anything with a 1000 watt real world draw.

      • Bauxite
      • 7 years ago

      Most racks (filled with servers) use fairly conventional power supplies.

      Besides usually having redundancy, fast (noisy) fans that run at full blast 24/7, and varying configurations of internal connectors that boil down to the same voltages in different pinouts all stuffed into different form factors of metal boxes, nothing special or really different than “standard” PC power supplies.

      You might run into DC-DC units or non-household voltage/amperage in some server farms but theres no real magic there either.

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