Antec not that bad!!

srbliss · Post by **srbliss** » Tue Feb 10, 2009 10:14 pm

I am using the Antec NSK 1380 and just replaced the stock 80 Plus power supply with a Pico 120W unit. I was hoping for a nice 10 watt decrease in idle power. I only got 3 watts. It is much quieter (from very quiet to silent) but I was really hoping to see idle at under 30 watts. Idle went from 37/38 to 34/35 watts.

Steve

jessekopelman · Post by **jessekopelman** » Wed Feb 11, 2009 1:03 am

Yes, seems like your Antec is actually making 80% efficiency even at this very low draw. Really, I think this is in keeping with what others have found -- it is not really worth it to go from an 80+ PSU to a Pico just in the hopes of power savings. Noise is a different issue, but at such a low draw you could swap for a very slow PSU fan and save some money.

DragonMaster · Post by **DragonMaster** » Wed Feb 11, 2009 4:25 am

Many power bricks probably aren't that efficient...

You've probably only saved on fan power

jessekopelman · Post by **jessekopelman** » Wed Feb 11, 2009 2:17 pm

DragonMaster wrote:Many power bricks probably aren't that efficient...

You've probably only saved on fan power

Not true. Most 12V bricks are 90+% efficient. The problem is this: Say your brick is 95% efficient and your DC-DC part is 95% efficient, your end result is only 90% efficient. That is pretty much the best case scenario. More likely, you are at closer to 90% for brick and 95% for DC-DC, giving you a composite of ~86% efficiency. But going back to the best case scenario, what is the difference between 80% efficiency and 90% efficiency at very low draw? Let's say your DC demand is 30W. 80% efficiency means AC demand of 37.5W, while 90% means AC demand of 33.3W -- so you've only saved 4W by going to pretty much the highest practical efficiency.

The draw of the PicoPSU is that we know that we are going to get 85+% efficiency with any decent brick at even very low draws. Meanwhile, 80+ PSU are only tested down to 20% utilization, which is often 60W or higher, so how do we know what efficiency we get at 30W? Still the difference between 70% efficiency and 90% efficiency, with a demand of 30W, is only 10W. If your DC demand is even lower, so will be the benefits of increased efficiency. So, it is very hard to cost justify a PicoPSU on energy savings alone. Meanwhile, low demand means little heat in the PSU even at relatively low efficiency, so swapping for a very low speed fan is a no-brainer. Thus, noise reduction is also not a good argument for a PicoPSU. That still leaves us with is the desire for a case too small to accommodate an internal AC-DC unit as a good reason for PicoPSU. Another good reason to use a PicoPSU is if you want to run directly from battery power rather than AC.

Plekto · Post by **Plekto** » Wed Feb 11, 2009 5:37 pm

Also, moving the heat source outside of the CPU is a big secondary bonus. The old Atari, Commodore, and similar 8 and 16 bit computers commonly had a big power brick. As a result, the systems could be run mostly passively and still last well over a decade. All while being silent.

Also, with no PSU, it's possible to drop the entire thing into a typical desktop/mini type case designed just for this and save a load of space. Toss in a second 120mm fan or similar into the PSU rear opening(tiny bit of plastic or metal fabbing at most) - instant 2x80mm or 2x120mm at 5v case no bigger than a small speaker.

viewtopic.php?t=49401
Or you can do stuff as advanced as this, since you're free of the PC form factor.

DragonMaster · Post by **DragonMaster** » Thu Feb 12, 2009 9:28 am

If size isn't an important factor, is the picoPSU at least able to solve this :

On one of my old (and heavy) systems, I installed an FSP Zen 300W, and it won't start unless I connect many fans to it since the system doesn't require enough power on the 12V rail. Once the system has started, if I disconnect a fan or the HDD, the PSU turns off.

Here's what uses power in that system:
P3 800MHz Socket 370
Stock AMD Socket A CPU heatsink fan
Gelid 92mm fan (0.1A at 12V)
Asus CUV4X
TNT2 M64
512MB SDRAM
2x 3Dfx Voodoo2 in SLI
Yamaha XG soundcard
3Com 3C905B
USB 2.0/Firewire PCI card
MusicQuest MQX-32M MIDI interface
Mitsumi CD-ROM
Asus CD-RW
Mitsubishi 5Â¼" FDD
(can't remember) 3Â½" FDD
iomega ZIP100 IDE drive
Maxtor 20GB HDD

That system hasn't a single empty space left and still manages not to boot unless I connect an 8W Papst double-ball bearing fan probably producing over 40dB of motor whirring and air noise.

Are old computer not making use of 12V at that point?