180W PSU for a P4 system??

ellroy80 · Post by **ellroy80** » Thu Jun 16, 2005 10:33 pm

G'day,

Just wanted your thoughts on a PSU that I am thinking of using. Do you think this (http://www.sparklepower.com/pdf/FSP180-60SAV.pdf) would be enough to power a system consisting of the following:

P4C800-E, all excess components of mobo (i.e. sound, RAID etc) turned off
P4 3.0 Northwood
1 gig RAM (2 x 512)
1 HDD (10 gig Seagate out of Xbox)
Old PCI vid card (1-2 mb S3 Virge I think)

I have had a quick think about it, I think I am probably sitting right on the edge but I can't gauge it, mainly cos of the mobo. So I thought I'd pose the q to all you PSU guru's.

FWIW this is the same PSU that is used in the AOpen H340 cases. Anyone running a similar system (i.e. i875) in one of these?

madman2003 · Post by **madman2003** » Fri Jun 17, 2005 12:01 am

I probably can't give you a definitive anser, but i'll try to help.

According to this: http://www.cpuheat.wz.cz/html/Pentium4.txt

Your cpu uses 62w or 64w. (12v line)

The rest i'm mostly basing on this: http://takaman.jp/D/index.html?english

Motherboard: +/- 23 w(3,3v:10w 5v:10w 12v:3+w)
Memory: 8 w (5v line)
Harddrive(assumption it's a ST310014ACE): +/- 28w (5v: 5w 12v: 23w) <-- worst case scenario for a hard drive
Videocard: 20 w (i took the number of a gf2mx, yours probably uses less) (5v line)

Total: 3,3v: 10w --> +/- 3 amps
5v: 43w --> 8,6 amps
12v: 90w --> 7,5 amps

If there are no other big power eaters present, (i didn't account for fans and maybe an optical drive, but that shouldn't be too much of an issue) then i would try it. But i can't be sure. I am assuming that the psu delivers what it promises.

Elixer · Post by **Elixer** » Fri Jun 17, 2005 1:56 am

It will probably work, but it probably won't be very quiet.

jojo4u · Post by **jojo4u** » Fri Jun 17, 2005 2:54 am

With this video card it should be ok. Depends on the quality of the PSU.

cjpark · Post by **cjpark** » Fri Jun 17, 2005 4:22 am

I've got a 3.2 northwood at 3.3ghz w/ a gig of ram, sound card, hard drive, dvd burner, x800pro (used to be 9800xt) and a few fans on a 250w, but its a seasonic w/ active pfc. I'd think you'd probably be alright as long as you don't put much else in there.

ellroy80 · Post by **ellroy80** » Fri Jun 17, 2005 7:52 am

Thanks for the replies everyone. I think I am pushing it, that PSU supplies only 10A on the 12V rail. The CPU uses around 90W, HDD requires 23 W at startup, so I'm already at 9A. Too close for comfort for me.

Anyone use Inwin PSU's before? I'm looking at their 240W version. I would love a Seasonic 250 or 300W, but there is apparently no Aussie distro

. BTW noise isn't an issue, that's what modding is for!!

Devonavar · Post by **Devonavar** » Fri Jun 17, 2005 9:28 am

My answer would be yes, it's probably enough. Where did you get that 90W figure for the CPU? IMO, madman's 62/64W estimate sounds more reasonable to me, although I'm just basing this on memory right now.

alglove · Post by **alglove** » Fri Jun 17, 2005 10:31 am

Going to http://processorfinder.intel.com shows all the 3 GHz Pentium 4 CPUs with thermal design specs in the 80W-90W range.

Devonavar · Post by **Devonavar** » Fri Jun 17, 2005 10:50 am

alglove wrote:Going to http://processorfinder.intel.com shows all the 3 GHz Pentium 4 CPUs with thermal design specs in the 80W-90W range.

You're right. His processor is listed as ~81W. I still think the 180W PSU could handle it, but it looks like he's chosen to be conservative.

ellroy80 · Post by **ellroy80** » Sat Jun 18, 2005 7:54 am

Devonavar wrote:
alglove wrote:Going to http://processorfinder.intel.com shows all the 3 GHz Pentium 4 CPUs with thermal design specs in the 80W-90W range.
You're right. His processor is listed as ~81W. I still think the 180W PSU could handle it, but it looks like he's chosen to be conservative.

Yeah, but like I said, only 10A on the 12V rail is a real downside. As this machine will be a folding boxen, it will be using all of those 81W for the CPU, all the time. So there's 7A for the CPU gone, leaving only 3A for a HDD, mobo, and whatever else.

One q, sorta off topic - does the manufacturers specs take efficiency into account? For example, this PSU is 180W at 70% efficiency. Does that mean that the actual output is 126W? If so, does the same hold true for the different currents on the various rails (i.e. 10A rail is really only putting out 7A)?

Post by **MikeC** » Sat Jun 18, 2005 8:23 am

ellroy80 wrote:One q, sorta off topic - does the manufacturers specs take efficiency into account? For example, this PSU is 180W at 70% efficiency. Does that mean that the actual output is 126W? If so, does the same hold true for the different currents on the various rails (i.e. 10A rail is really only putting out 7A)?

180W is the OUTPUT. 70% efficiency means the input (AC power in) would be 180 divided by 0.7 = 257W.

Agreed that the Fortron PSU would be borderline for longevity, thogh I think it would work. Something with more like 15A on the 12V line would be better.

ellroy80 · Post by **ellroy80** » Sat Jun 18, 2005 7:48 pm

MikeC wrote:
ellroy80 wrote:One q, sorta off topic - does the manufacturers specs take efficiency into account? For example, this PSU is 180W at 70% efficiency. Does that mean that the actual output is 126W? If so, does the same hold true for the different currents on the various rails (i.e. 10A rail is really only putting out 7A)?
180W is the OUTPUT. 70% efficiency means the input (AC power in) would be 180 divided by 0.7 = 257W.

Agreed that the Fortron PSU would be borderline for longevity, thogh I think it would work. Something with more like 15A on the 12V line would be better.

Thanks for clearing that up Mike.

I had a thought last night, that the huge amount of power required for the HDD is only required to start it up, right? Well that only happens when the machine is turned on, and at that time the CPU isn't loaded, so it isn't going to be drawing its full amount of power. Once it is 100% loaded the HDD will already be spun up, using less power, which means it would probably be alright with this 180 watter, right?