What are my probable PSU needs?

Korea Beat · Post by **Korea Beat** » Wed Oct 07, 2009 5:47 am

Hi everyone, this is my first post, so sorry if this is the wrong sub-forum.

I'm thinking about going completely passive with my old Socket A system, which still meets all my needs since I'm not really interested in newer games. I think this should work with a Thermaltake Sonic Tower for the CPU, and some form of fanless PSU. I'm worried about the case heat that would be generated by a truly fanless PSU though, so something like the PicoPSU is pretty attractive. But then I worry whether that can deliver enough power.

Here's the set-up:

AMD XP 2400, passively cooled
VIA KT133A motherboard
1.5Gb PC-133
120Mb 2.5" 5400RPM Hitachi
Creative Audigy 2 ZS
Geforce 6800 (Gigabyte's passively cooled version)
DVD-ROM
Floppy drive

Am I in safe territory, or heading towards the danger zone?

bonestonne · Post by **bonestonne** » Wed Oct 07, 2009 6:07 am

I would say go for like, 150W power supply, PICO should work out. I wouldn't comment on efficiency though because of its age...

I think you'd be fine though, you don't have any power hungry components, so it should be fine

kater · Post by **kater** » Wed Oct 07, 2009 6:31 am

I was recently upgrading my girl's PC - she had an Athlon like yours, an MX440 (or some such) VGA, 1 HDD, 1 ODD + the usual stuff. In idle, with a good FSP MDN Rev A PSU her PC drew 110W, when the CPU was loaded it slightly exceeded 140W. So no big needs here.

The 6800 you have might make things more complicated tho :/ Does it have an auxiliary molex power connector? In all probability you're looking at additional 50-60W here, under load.

BUT!

Remember that such setups draw mostly from 5V. Unless your mobo has a P4 connector. But most of such systems need somewhat beefier 5V lines than contemporary PCs. So a Pico or a DC/DC is probably too small in these terms for your needs as they have big 12V lines and only a few watts on 3.3V and 5V lines.

bonestonne · Post by **bonestonne** » Wed Oct 07, 2009 8:53 am

I agree with that. The only athlon system I ever had was just for a few days, and I gave it to a friend at the time, because his emachines was fried.

If you get the 150 or 180W PICO you shouldn't have any problems under a normal load, but using superpi or orthos for any extended periods of time would be a bad idea.

Michael Sandstrom · Post by **Michael Sandstrom** » Wed Oct 07, 2009 10:44 am

SPCR forum members have found the Extreme Power Supply Calculator web site to produce numbers very close to actual Kill-A-Watt or Seasonic Power Angel readings.

Post by **CA_Steve** » Wed Oct 07, 2009 1:11 pm

I stuck a Kill-a-Watt on the back of my secondary-nearly-always-unplugged PC for some measurements. It's a barton 2800+ with an Abit NF7-S mobo (NForce2 chipset), 1 HDD, 2 DVD drives, floppy, and a passive 6600GT in a Sonata case with the TRU380W PSU. The 6600GT idle power is about the same as a 6800 and it uses maybe 10W more than the 6800 in 3D.

At the wall:

boot power (max seen) 137W
idle 115W
playing WoW 145W
prime95 139W
furmark 150W
prime95+furmark 160W

Estimated power draw from PSU, given efficiencies from review (~65% at this power level):

boot power (max seen) 89W
idle 75W
playing WoW 95W
prime95 90W
furmark 97W
prime95+furmark 104W

That should give you a feel for the power required. You'll have to work out whether the PSU you want can supply enough 5V and 12V amperage.

Korea Beat · Post by **Korea Beat** » Wed Oct 07, 2009 5:15 pm

Thanks for all the advice guys. Looks like I will probably use a conventional PSU but make some modifications to the case for better airflow. With some careful experimenting I can probably get this to work.