Seasonic M12D 750w ATX PSU Page: 1
Introduction

When it comes to silent yet powerful PSU's, Seasonic are often one of the first companies to be mentioned. In business for almost 35 years, Seasonic certainly know what they are doing when it comes to manufacturing power supplies with some of their previous models having reached an almost iconic standing among the silent PC community.

However, despite Seasonic having a full range of retail PSU's, some of which we've reviewed in the past, Seasonic's primary business is in OEM - building PSU's to spec for companies such as PCP&C and Corsair. Therefore, the release of their own models is often few and far between making the chance to review one an opportunity I'd certainly never pass up.

In case you hadn't already guessed, today's subject is going to be the M12D 750w. Released at the tail end of 2008 the M12D is a modular unit that builds on the features of the original M12 600w unit that I had the pleasure of reviewing just over two years ago. However, over the course of two years a lot has happened in the world of OC3D PSU testing and today the M12D is going to be facing a wrath of our SunMoon load tester combined with a toasty 50°C oven. But let's not get ahead of ourselves and instead start off with some specs pulled from Seasonic's website:

• Super High Efficiency (up to 90%) - Green solution for lowering energy consumption, noise & heat.
• DC to DC Converter Design - Superior dynamic response & greater system stability.
• Practical Dual +12V Rails - Ample +12V output with OCP for extreme utilisation.
• Tight Voltage Regulation - Improved load regulation to reduce voltage variations.
• Highly Reliable 105°C Japanese Brand Capacitors - Exceptionally reliable components extend product life.
• Solid Caps on 12Vs for Extreme Stress Operating Conditions - Enhanced stability at severe operating conditions.
• Active Power Factor Correction (99% PF) - Reduces line loss & power distortion.
Dual Sided PCB Layout - Better utilisation of PCB space to enhance quality and performance.
Detachable Modular Cables - Flexible cable solution to reduce clutter.
San Ace Silent Fan (Sanyo Denki) - Premium quality fan for silent operation.
Smart & Silent Fan Control (S2FC) - Smart thermal control to balance between noise & cooling.
Ultra Ventilation (Honey Comb Structure) - Minimises airflow resistance for maximum cooling.
Multi-GPU Technologies Supported - 6P and 8P PCI-E connectors to support all multi-GPU platforms.
All-in-one DC Cabling Design - Supports PC, IPC, workstation, and server systems.
Universal AC Input - Plug & run safely anywhere in the world.
Patented Easy Swap Connector - Unplug the connectors easily, quickly, and safely.
5 Year Warranty - Our commitment to superior quality.

Aaaand breathe! Phew. Quite a long list of features there with Seasonic including everything from the shape of the ventilation mesh to the manufacturer of the cooling fan! But hey ho - if you've got it, flaunt it! Right?

Out of all the features the most prominent one of all has to be the 90% efficiency. Only a hand full of units out there at the moment can actually achieve this and it will certainly be interesting to see if we can get anywhere close to this during our testing. Other interesting points also have to be the Japanese 105°C caps and support for 'all' multi-gpu configurations; but I'll have a closer look at those over on the next few pages.

Seasonic M12D 750W Rail Layout
DC Output +3.3V +5V +12V1 +12V2 +12V3 +12V4 +12V5 +12V6 -12V +5VSB
24A 30A 36A 36A - - - - 0.8A 3A
Max Power 150W 744W 9.6W 15W
750W

What a lovely pair......of +12v rails we have. Each with an individual maximum capacity of 36A and a combined max capacity of 744W (62A). Of course once you start placing load on the +3.3v and +5v rails, this eats into the +12v output somewhat (remember its 'only' 750W total), but for almost all mid to high end PC's the configuration should be perfect.

Now lets move on to the next page where we take a look at the unit in all its glory..


Seasonic M12D 750w ATX PSU Page: 2
Packaging & Appearance

While most manufacturers tend to go for the loud and lary approach to packaging their products just so that they stand out on retailers shelves, Seasonic have defiantly swung in the opposite direction by opting for a very professional 'pipe and slippers' look based on a black and orange theme. At the front of the box clutter has been kept to a minimum with only a picture of the unit, the model number and a few other non-intrusive specification stickers dotted around.  While at the back we have the same full feature list as seen on the previous page along with a power distribution diagram.

Seasonic M12D Packaging Front Seasonic M12D Packaging Back
 
Protection for the M12D is quite minimal with only a bubblewrap bag and a single walled layer of card keeping it safe from the outside world. This is in stark contrast to the the likes of Corsair and Cooler Master who tend to encase their PSU's in large lumps of moulded styrofoam that act almost like kevlar jackets. In fact, even the modular cables seem to have cut a better deal than the PSU in packaging department; getting their own separate compartment and a drawstring bag.

Seasonic M12D 750w Box Open Seasonic M12D 750w Contents
 
The unit its self measures in at a pretty standard 150x160x86mm and is finished in a black powdercoat. This ensures that it fits a wide range of smaller PC cases including some HTPC's and doesn't stick out like a sore thumb in a standard 'non-blinged out' PC build.
 
Seasonic M12D 750w Side Seasonic M12D 750w Front

At the rear you will find the usual kettle lead socket and power switch along with a honeycomb grill common to 120mm+ fan cooled PSU's. Thankfully the switch and socket are mounted upon a solid area of metal rather than the mesh, meaning that the casing is less likely to flex or bend if you happen to be a bit heavy handed when plugging in the power cord.

Rather than attempting to shoe horn in a 135/140mm fan, Seasonic have stuck with a tried and tested 120mm model. I'll get on to the finer details of this fan over the next page, but providing Seasonic have chosen wisely; it should still be able to compete with the Noise/CFM ratio of a larger model.

Seasonic M12D 750w Rear Seasonic M12D 750w Fan
 
Finishing up with the modular connector panel, Seasonic have fitted the M12D 750w with a total of 6 sockets for plugging in cables. Two of these are reserved for PCI-E connectors while the other four can be used for any combination of IDE or SATA connectors. From left to right the rail layout used on the connectors is +12v2, +12v1, +12v2, +12v2, +12v1, +12v1.

Seasonic M12D 750w Modular Seasonic M12D 750w Connectors
 
Lets flip over to the next page and check out what cables are included, along with what components Seasonic have used inside the unit.


Seasonic M12D 750w ATX PSU Page: 3
Cables & Internal Layout

'Hybrid modular' is the name of the game on the M12D with the bare minimum cables required to get your PC up and running being already hard-wired into the unit. This has the advantage of providing some of the most important cables (ATX/EPS/PCI-E) with a direct connection to the PSU's power while also removing the potential for any dodgy modular connectors to add resistance to the circuit. It does however come at the cost of the PSU not being fully customisable by the user.

Seasonic M12D 750w Hard wired Seasonic M12D 750w hard wired

In the case of the 750w model Seasonic have hard wired  1x ATX, 1x EPS12v, 1x P4-12v, 2x PCI-E and 3x SATA connectors to the unit. Both the ATX 24-Pin and PCI-E 8-Pin connectors can be reduced down to 20-Pin and 6-Pin connectors respectively to support a wide range of motherboards and graphics cards, whereas the EPS12v 8-Pin connector is not interchangeable and for this reason Seasonic have included a separate 4-Pin P4-12v connector for older motherboards.

Seasonic M12D Main Cables Seasonic M12D PCi-E

A total of 8 modular cables are included, which is plenty for a modular system that can only support up to six cables being plugged in at any one time. Of course two of these connectors are dedicated to PCI-E only, which means that...yes, unlike the OCZ Fatal1ty 700w I reviewed last week...the M12D can support high-end dual graphics card configurations.

Seasonic M12D 750w Cables Seasonic M12D 750w Cables
 
Moving on to the more juicy stuff, removing the lid of the M12D reveals a reasonably tidy internal layout with two massive aluminium heatsinks running in parallel along the length of the unit. Hidden beneath the heatsink at the lower part of the picture (below-left) are several inductor coils that perform the PSU's PFC and AC transient filtering. The heatsink towards the top of the picture also hides some goodies; namely the +3.3/5.0v voltage regulation module and the huge bunch of cables that enter the unit.

Seasonic M12D 750w Inside Seasonic M12D 750w Heatsink

Seasonic M12D 750w Inside Seasonic M12D 750w Side
 
Two transformers take centre stage in the unit with the larger of the two responsible for the +12v rail, and the smaller being soley responsible for the 5vsb (standby voltage) rail. Over to the right of these are two large capacitors manufactured by Japanese company Nipon-Chemicon. The transformers carry specification markings of 400v / 390uF / 105c which shows that Seasonic haven't skimped on quality.

Seasonic M12D Trasnformers Seasonic M12D 750w Capacitors

The Sanyo Denki San Ace 120mm fan carries a model number of 9S1212H403, and despite details being pretty thin on the ground when I did a search of google, it appears to be capable of pushing 83CFM at <36dbA. Observant  people may have also seen the fan is actually fitted with a sheet of clear plastic on the exhaust side. This is probably to deflect airflow, making better use of air that would have normally exited straight out the back of the PSU.

Seasonic M12D 750w Fan Seasonic M12D Fan
 
Now let's pop the lid back on and get down to some testing...


Seasonic M12D 750w ATX PSU Page: 4
Simulated Load Testing

To provide our readers with the most accurate results, Overclock3D uses a professional grade SunMoon SM-268+ ATE load tester capable of placing a sustained load of 1690w across a total of six rails (including +5vsb and -12v) on the PSU. Unlike our previous resistor-based load tester, the SM-268+ gives us the ability to adjust amperage loads in increments as small as 0.01A while also measuring voltages and wattage readings on-screen.

During today's tests, we will be placing the M12D under 25%, 50%, 75% and 100% load levels at both room temperature and inside a hot box regulated to a temperature of around 50°C. Additional cross load tests will also be performed under these conditions to simulate how the PSU would perform with a heavily uneven distribution of load.

Seasonic M12D 750w SM-268+ Results @ Room Temp
  +3.3v +5.0v +12v1 +12v2 +5vSB -12v AC Watts /
 DC Watts
 Efficiency Intake /
 Exhaust
Δ Temp
Test 1
(Low)
 5.50A 3.75A6.25A6.25A 0.75A 0.20A 226w /
 199w
 88.05% 22.6°C /
 25.2°C
 2.6°C
 3.35v4.96v12.45v12.43v 4.99v -12.40v
Test 2
(Med)
 11.00A 7.50A 12.20A12.20A 1.5A 0.40A 431w /
 388w
 90.00% 23.1°C /
 29.4°C
 6.3°C
3.30v4.91v12.37v12.35v 4.94v -12.41v
Test 3
(High)
16.50A 11.25A 18.75A18.75A 2.25A 0.60A 662w /
 588w
 88.82% 23.9°C /
 31.5°C
 7.6°C
3.24v4.86v12.27v12.26v4.89v -12.47v
Test 4
(Full)
 22.00A 15.00A 25.00A25.00A 3.00A 0.80A 885w /
 782w
 88.36% 24.5°C /
 32.8°C
 8.3°C
3.19v4.80v12.18v12.20 v 4.84v -12.55v
Test 5
(x-load)
23.00A20.00A0.50A0.50A0.75A0.20A 233w /
191w
81.97%20.2°C /
26.5°C
 6.3°C
3.27v4.87v12.45v12.44v4.96v-12.45v
Test 6
(x-load)
 3.00A 5.00A 31.00A31.00A 0.75A 0.20A 906w /
801w
88.41% 23.5°C /
 31.6°C
 8.1°C
3.25v4.87 v12.18v12.19v4.92v -12.84v

*slobbers*...do you see what I see? Yes the 90% efficiency at a DC load of 388w is not a typo and come in at just the kind of load level the average enthusiasts PC system is likely to run at when under a light stress. The rest of the results also back up the M12D's 80-PLUS Silver certification with an average of 88% efficiency being recorded throughout all of the non-crossload testing.

Unfortunately it's not all good news though as the M12D puts out some slightly shady voltages in Test 1 with the +12v rails bordering on 12.45v. Test 2 and 3 manage to bring these voltages down a tad with the additional load being placed on the PSU, but throughout the testing I couldn't help but notice all the voltage outputs bouncing around like a 5yr old who's just downed a can of Red Bull. Seriously, it was quite hard to take a reading without it flicking over to another number +/-0.03v either side of what I'd begun writing down.

Seasonic M12D 750w SM-268+ Results @ 50°C
  +3.3v +5.0v +12v1 +12v2 +5vSB -12v AC Watts /
 DC Watts
 Efficiency Intake /
 Exhaust
Δ Temp
Test 1
(Low)
 5.50A 3.75A6.25A6.25A 0.75A 0.20A 226w /
 199w
 88.05%50.5°C /
54.5°C
 4.0°C
 3.35v4.96v12.45v12.43v 4.99v -12.40v
Test 2
(Med)
 11.00A 7.50A 12.20A12.20A 1.5A 0.40A 431w /
 388w
 90.00%52.0°C /
54.2°C
 2.2°C
3.29v4.91v12.36v12.33v 4.94v -12.41v
Test 3
(High)
16.50A 11.25A 18.75A18.75A 2.25A 0.60A 660w /
 588w
 89.09%50.9°C /
56.5°C
 5.6°C
3.24v4.85v12.27v12.26v4.88v -12.48v
Test 4
(Full)
 22.00A 15.00A 25.00A25.00A 3.00A 0.80A 885w /
 782w
 88.36%51.8°C /
59.7°C
 7.9°C
3.19v4.79v12.18v12.29 v 4.82v -12.56v
Test 5
(x-load)
23.00A20.00A0.50A0.50A0.75A0.20A 233w /
190w
80.85%50.6°C /
55.5°C
 4.9°C
3.26v4.87v12.45v12.44v4.96v-12.45v
Test 6
(x-load)
 3.00A 5.00A 31.00A31.00A 0.75A 0.20A 906w /
801w
88.41% 50.0°C /
58.6°C
 8.6°C
3.25v4.87 v12.17v12.16v4.92v -12.84v

Things didn't get any better for the voltage stability in the 50°C testing either (why would they?) with most of the voltage readings being around -0.01v lower than the room temperature tests, and still fluctuating. One thing that did have me grimacing slightly was the -12v rail in Test 6 which hit -12.84v. Sure it's nowhere near as likely to do damage as the +12v rails, but some better regulation wouldn't have gone amiss.

Efficiency managed to stay almost exactly the same with that magical 90% still being achieved in Test 2 despite the PSU components being under a lot more stress due to the increased temperature.

Seasonic M12D 750w Scope Results @ 50c
  +3.3v +5.0v +12v1 +12v2
Test 1
(Low)
T1_3.3VT1_5VT1_12Vt1_12v2
Test 2
(Med)
t2_3.3vt2_5vt2_12vT2_12V2
Test 3
(High)
t3_3.3vt3_5vt3_12vt3_12v2
Test 4
(Full)
t4_3vt4_5vt4_12vt4_12v2
Test 5
(x-load)
t5_3.3vt5_5vt5_12vt5_12v2
Test 6
(x-load)
t6_3.3vt6_5vt6_12vt6_12v2

Both the +3.3v and +5.0v rails managed to put out some nice clean lines on the scope, with ripple staying below 8mV in most cases and only hitting as high as 11mV in test 4 and 5. The +12v1 and +12v2 rails on the other hand were giving me crazy eyes with the scope set to 2ms, producing some weird patters that I've never come across before.

Slowing things down to 5ms readings gave a clearer picture of what was going on with ripple staying below 43mV throughout the testing. Not bad at all, even though I have had better elsewhere darling.


Seasonic M12D 750w ATX PSU Page: 5
Conclusion

OK so we've pulled the M12D apart, poked at it, put it through hell on our SM-268+ load tester and stuck it in a box hot enough to keep your roast dinner warm. But how did it perform?

Starting with efficiency the M12D 750w certainly did not disappoint. In almost all tests 88%+ was easily achieved by the unit with Test 2 (388w) even managing to hit 90%. I don't think I need to tell you how awesome this is as there are very few units on the market that can come close to this level of efficiency throughout every load level. The fact that the results remained steadfast inside our toasty 50°C hot box just further reinforces the point.

Although getting any official noise readings from the unit is quite difficult with all of the PSU testing equipment whirring away in the background, the M12D appeared to be completely inaudible until the loads levels of Test 3 (588w) were introduced; at which point the fan could just about be heard. Based on the relatively small number of PSU's I've tested with our new equipment so far (Corsair TX850w / OCZ Fatal1ty 700w / ASUS U-75HA) I'd say that the M12D is most certainly the quietest of the bunch.

Overall voltage stability was quite good with the +12v rails only shifting by 0.27v from Test1 to Test4 and similarly the +3.3v and +5v rails only shifting 0.16v respectively. Unfortunately the idle voltage levels were of a slight concern on the +12v rails, starting quite high at around 12.45v in Test 1. Although this is certainly within ATX spec and of no danger to damaging hardware, the mark of a quality PSU in my opinion at least is how close it can stay to 12.00v at all load levels.

ADDENDUM:
Seasonic has responded to these results stating that they are uncharacteristic of this model. They have reproduced our load tests on their own equipment using an M12D from a different batch and the idle voltage levels are much lower. Due to time restraints we have been unable to obtain a different sample for testing, but should one become available in the future we will update this review with the revised results.

Finishing up with the scope output it's getting quite hard not to repeat everything I've said on the previous page. However, with the +3.3v and +5v rails staying below 11mV and the +12v below 43mV the results place this as one of the cleanest and greenest PSU's tested to date.

Coming in at £149.49 over at Scan, the M12D is at the high-end of what would be considered acceptable for a PSU of this wattage. In fact it would be short sighted not to point out the wide range of 800-1000w PSU's available for a similar price. However, while most of these can match the unit in some areas, the M12D represents a new breed of PSU that combines super-high efficiency with all the additional qualities of a top-end PSU. So for some, the additional outlay might be worth it in the long run.


The good
- Low ripple & noise on scope.
- Ultra high efficiency backed by 80PLUS Silver certification.
- Hot box testing produced near identical results to room temperature tests.
- Quality components - right down to the San Ace fan.
- 4x PCI-E connectors.
- 5yr Warranty.

The mediocre
- Average packaging for such an expensive PSU.
- Price quite high.
- Voltages on the +12v rails idle quite high.

The bad
- Nowt


Overclock3D Performance Award

Thanks to Seasonic for providing the M12D for review. Discuss this review in our forums.