Hardware First Look: Seasonic M12D 850W PSU

http://www.bit-tech.net/hardware/2009/01/04/preview-seasonic-m12d-850w-psu/1

Seasonic breaks its own mould with the highest power unit it has ever launched. That's not what's special though - the ultra high quality fan and 80Plus Silver efficiency rating could very well raise the PSU bar again.

 

I would prefer to have either all modular PCI-E cables, instead of this 2+2 configuration.

Anyway, looks like a nice PSU.

 

At that price competing against Corsair / Antec won't be easy...
Sure, Seasonic has a reputation for high quality psu's, but even for them 300 seems too much.

 

"yay or neigh" There a horse in the office?

-- 'yea or nay'

 

Wow It seems like all PSU are going modular now. I still think the Ultra X3 ULT40312 850-Watt is the best PSU out there 100% modular!!

 

No, a Camel

 

Finally, someone said it!

I`m no electrical expert, but i just got confused when other sites were recommending 1000W+ PSUs, while a QX7000 OC`ed and a HD4870X2 in were only consuming something like 500-600W peak wattage. So these are just cases where we need to apply our BS filter, right?

 

Not really - most PSUs optimal efficiency is about the 50-75 percent range, so for 500-600W system an 850-1,000W PSU is pretty good, but few people own multi-GPU high end.

 

Seems like that sweet spot that the higher-end people were looking for in terms of a modular PSU that wasn't 1600+ Watts or so. I'm pretty sure this is a perfectly fine PSU as well. Seasonic has a bit of a reputation.

 

Hey, thx for the reply.

But i`m still a bit confused regarding efficiency:

I also assumed that for a 50% efficiency (just using a low round number for easier comparison), if your system needed 300W, you would have to have at least a 600W PSU. But from what i read a while ago (don't remember the site exactly), i understood something like this: If you have a 500W with 50% efficiency, it DOES provide 500W, but it draws 1000W from the wall socket, therefore increasing your electric bill. Again, i`m exagerating with the percent, for easier comparison.

I am also puzzled about the fact that my PSU is 280W, and i used an HD4870 512MB and 2x HD4850 CrossFire on my EP45-DS3 with my trusty E2140, running at 3.2GHz (100% OC) and I didn't have any problems. No artefacts, no restarts. I also tested my system with a Gigabyte Superb 720W and i got the same results. By my calculations, my PC should've ran out of juice with my regular PSU

Can you explain pls?

 

He means PSUs are most efficient at converting wall power into usable power (therefore running cooler and wasting less electricity) when they're 50-75% loaded.

280W is probably the power draw of a generic system with a 4870X2 installed so you're at the limit but not over it (check the reviews where it says total power consumption of the system with the GPU installed).

No, you need a 300W PSU but it'll draw 600W from the wall (therefore wasting 300W which heats up your system and costs money).

 

Lets take a 500W PSU for example:

If the PSU was "50% efficient" (very poor) => 500W output by the PSU itself (500W being drawn by the system to CPU, graphics, HDD etc - and FULLY LOADING the PSU) = 1000W required at the wall socket. Therefore, that extra 500W more is being lost between AC socket and your components as heat.

Now, normally instead of "50% efficient", PSUs these days pull 80, usually 85+% efficiency for good ones, meaning fully loading a 500W PSU will cause 575W to be drawn at the wall, losing only 75W as heat. Likewise, fully loading a 1000W PSU at 85% efficiency = 1150W at the wall, 150W lost as heat - twice as much lost for twice as much power used.

The "efficiency curve" is measured across the load scale - normally the 80Plus program uses load levels that are 20% (idle), 50% (typical) and 100% (full). For a 1000W PSU those load levels equate to 200W, 500W and 1000W DC output (NOT at the wall socket).

The efficiency normally translates like this: ^ starts low, goes high in the middle, then dips again. Usually, a PSU reaches maximum efficiency at around half load (50%) but it depends on the design. Look at the bottom right hand picture here: http://images.bit-tech.net/content_images/2009/01/preview-seasonic-m12d-850w-psu/paper3-8.jpg

So, if we load a 500W PSU to 50% DC output, but it's 85% efficient we have:

500 x 50% = 250W PSU load (DC output)
250 x 1.15 (85% efficient = 15% loss) = 287.5W AC drawn at the wall.

Your 280W PSU should have blown its tits off tbh - you were lucky imo If it was built well it would have overcurrent protection and would just cut out.

 

Very nice explanation and first look and the PSU.
I bet you did the load tests, while you can't publish them, was the PSU actually 80+ silver ?

 

I haven't loaded it properly, otherwise I would have published the results. The only independent results we have are from the 80Plus certification.

 

Too bad this is a modular PSU , modular PSU are less efficient due to the extra unnecessary connectors , I will never buy a modular PSU , I can hide very easy all the cables at the back of the mobo tray of my coolermaster case , therefore modular PSU not necessary , I am choosing between the Coolermaster UCP 900W , the Silverstone OP-Evolution 850W Olympia , or the new Corsair TX850W , I love the non modular PSU, professionals don`t use modular PSU

 

You're kidding, right?

The efficiency barely takes a hit due to the modular cables if at all. I'd try a Google search.

Professionals don't use modular PSU's, huh? Take a look in the project logs!

 

Meh, that's mostly FUD and elitist PC Power and Cooling talk.

How come the MODULAR be quiet PSU tops our efficiency list? And this Seasonic does incredibly well also? And the Antec Signature, which is semi modular, does better than the CM UCP 900 at 20% load?

To be honest - not using 16 AWG (or thicker) wire has more or as much potential effect on efficiency as a modular connector. As long as it's well made and the connection is secure, it's not an issue. Normally it's user error that's the problem but manufacturing faults can come into play to.

A few percent efficiency makes very little difference compared to the convenience of only using the cables you want and keeping your system cooler. If you have a case to pack them away neatly - good for you!! - most of us don't

 

Fortunately I have a case able to pack the cables away neatly , therefore modular PSU are not necessary

 

I will never buy a modular PSU because I want to keep a tidy case and the Modular PSU are messy with plenty of Ugly connections and silly LEDs

 

You're extrapolating a lot from a single example, especially when the Seagate ones are black and the case is black.

I don't understand how you claim modular PSUs are messy when they have less cables.