oc'd e6600 3.6 and 8800GTX powered from 380W PSU - why not?

mcoleg · Post by **mcoleg** » Sat May 19, 2007 8:11 pm

i've posted it on ocforums sometime ago:

http://www.ocforums.com/showthread.php?t=511180

i did some calculations and i arrived to a conclusion that this system:

1. 8800GTX alone = 132W full load, 70W idle.

2. e6600 @ 3.6GHz with 1.47v vcore actual = 135W @ 100% utilization.

source: http://www.extreme.outervision.com/p...ulatorlite.jsp

3. 4x1GB DDR2 RAM.

4. 2xSATA 7200RPM HHD and DVD burner.

5. P5W64 WS Pro motherboard.

6. 4 pretty low-power fans, including yate-loon slow inside the tuniq and whatever is inside of the 8800GTX.

7. misc. extension cards that come and go

8. PCP&C 750W Silencer

can be ran from this psu (seasonic-made antec ea380):

http://www.newegg.com/Product/Produc...82E16817371005

1 and 2 on the list above are the biggest draw of power, 3 to 7 really don't consume all that much. CPU and the video card then are the parts to worry about.

How much power does the whole system use? According to the Kill-A-Watt gadget from P3 International, PSU draws form the wall (I am rounding up):

At idle:

250W with 2A

Running CSS video test (I tried to spice things up by running orthos at the same time but the load didn't change):

380W with 3.2A

The 750W Silencer hits 80+ efficiency above 150W and keeps it till 600W load according to this review:

http://www.pcper.com/article.php?aid=37 ... pert&pid=5

Round up the efficiency to 80% and that will give us:

380W/5*4=304W of real power being consumed by the system under full load.

Give it a bit of a buffer to stay on the safe side and it looks like all I need is a 380W PSU for that system.

Now, a modern 380W PSU:

http://www.newegg.com/Product/Product.a ... 6817371005

let's see now. 2x12v rails, each at 17A.

the juice the components need to run at full load:

8800GTX - 132W/12V=11A

e6600 @ 3.6GHz - 135/12v=11.25A

Seems to be plenty left for whatever the rest of the system needs.

The PSU is rated to draw up to 6A form the wall. All my system needs is 3.2A at full load. So we seem to be safe there as well.

i went as far as getting one and running some tests as a prof of a concept.

now it's been running for 3 days under various loads and still lives

thoughts, comments?

jaldridge6 · Post by **jaldridge6** » Sat May 19, 2007 9:02 pm

I'm running a q6600 with an x550 on 380 watts, and have 180 watts to spare under full load with 4 sticks of RAM and 2 HD...

santacruzbob · Post by **santacruzbob** » Sat May 19, 2007 9:05 pm

that sounds reasonable. I've been powering an overclocked core duo system with a 7950GT KO on a 300W sparkle psu from ~1999. numbers don't mean as much as quality.

mcoleg · Post by **mcoleg** » Sat May 19, 2007 9:13 pm

wow, hard to impress you guys

jaldridge6 · Post by **jaldridge6** » Sat May 19, 2007 9:20 pm

well, buying a kill-a-watts really helped me get the facts on wattage usage and such. I am endlessly amazed at this massive power supplies that are out these days.

mcoleg · Post by **mcoleg** » Sat May 19, 2007 10:53 pm

well, there are big psu's and there are big psu's. as long as the load in the "goldilock's" zone for the psu's efficiency, it doesn't really critically matter if it's large than the system needs.

as i mentioned, i have a pcp&c750 and it's "goldilock's" zone is from 150 to 600w. my system pretty much stays there all the time while psu is operating at above 80% efficiency.

but yah, i do agree, some of the psu's out there are not really needed. no point in buying something one is not going to use.

jaganath · Post by **jaganath** » Sun May 20, 2007 1:15 am

mcoleg wrote:wow, hard to impress you guys

well, one of the fundamental principles of SPCR says "300W is enough for all but the most extreme setups", so you're preaching to the converted here. now if you could only hammer it into the thick skulls of the legion of l33t overclockers out there...

It is pretty impressive that you can run OC E6600 + 8800GTX on a <400W PSU; the only way to go more extreme than that is quad-core + SLI 8800GTX, which is just silly. I think the important thing to mention here is a it is a quality 380W unit, honestly rated.

Also, because we know we don't need as much power as everyone thinks, we can save money because the monster PSUs (>650W) are often two or three times the price of quality <400W PSUs.

mcoleg · Post by **mcoleg** » Sun May 20, 2007 8:02 pm

i do so agree with the last premise - lot's of money could be saved

e6600 @ 3.6GHz and 8800GTX is a pretty powerful workstation though, not that many people around here run something like that 24/7.

using a 380w psu with it is a prof of a concept; confirmation of some numbers i've put together.

the psu i've picked is far from the top models. as a matter of fact, i chose antec because they have exhibited a so-so build quality for some years now.
it did turn out to be of a higher quality than what we usually see from them though.

as far as the fundamental principle of SPCR that you mentioned - "300W is enough for all but the most extreme setups", it's all good and fine but look around - how many people actually follow it?

most folk that post in psu forum here end up with 430, 520 or even 600+ watt psu's even though their builds are not even close to be as powerful or power-hungry as mine.

that was one of the reasons i posted here. an irony, really - an overclocker trying to convince spcr's to use a lower-power psu

johno · Post by **johno** » Sun May 20, 2007 9:50 pm

The thing that annoys me a bit is that it's hard to find much in the way of power supplies with capacity less than 380W. It's like the minimum available one is bigger than the maximum needed.

The problem with this is that the efficiency is seemingly forgotten about for mainstream use. A modern office type PC need only draw about 35W from the power supply during normal use, which is less than 10% of the rated. However, Energy Star and 80 Plus certification only go down to 20% of full load - over twice the point that matters the most!

mcoleg · Post by **mcoleg** » Sun May 20, 2007 10:44 pm

johno, my system draws from the wall 340w on max load right now. that means it consumes around 270w which is only 70% or so of it's capacity.

that's why i've put the numbers together - to question my assumptions. 380w certainly doesn't seem like a powerhouse psu at a first glance, most ppl will shy away from it even for use in smaller pc's.

good point about Energy Star and 80 Plus certifications - they are not stringent enough, from what i hear.

jammin · Post by **jammin** » Mon May 21, 2007 8:25 am

Well done for jumping in and proving you can run a supposedly 'high power' system from what most would call a 'low power' PSU

I'm also trying to discourage the need for huge PSUs at the overclocking forum I frequent. Unfortunately I don't have the money to build a top of the line system in the first place so I can't do it first hand.

I think your thread will get a linking to.

And regarding the office type PC, what kind of PSUs do you think the big OEMs drop into their office systems?
I'd guess that they are less than 380W. If someone has access to one then feel free to report back.

Of course, that doesn't help people who are building their own systems.

johno · Post by **johno** » Mon May 21, 2007 8:33 pm

The 80 plus page shows a few lower power supplies that would be used by PC builders: http://www.80plus.org/manu/psu/manu_psu.htm. Among them, HP make a couple of 240W supplies. They're not something that seems to be stocked by the regular computer parts places though

jammin · Post by **jammin** » Mon May 21, 2007 11:39 pm

That's a helpful link

I've started a thread on the Overclocking forum I frequent to try to collect examples of systems running from lower powered PSUs.
If you know of any good examples then it would be helpful to post them

So far I've had one guy measure his power draw from this system:

Opteron 148@3ghz (1.6v core)
DFI LanParty SLI-DR (w/ Evercool VC-RE)
eVGA 7800GT (470/1100 stock clock)
2x1GB OCZ DDR500 3-4-4-8
2x80GB Hitachi SATA in Raid-0
4x12" UV CCFLs
2x4" UV CCFLs
~20 UV LEDs
4x120mm Fans (2 Panaflo L1s, 2 Tt low CFM)
2x92mm Fans (both Tt low CFM)
Pioneer 16x DL DVD-R/W

He came out at around 250W DC at maximum load assuming roughly 75% efficiency.

mcoleg · Post by **mcoleg** » Thu May 24, 2007 6:11 pm

jammin, sry for not replying earlier:

here's another link for you:

http://www.ocforums.com/showthread.php?t=512807

what overclocking forum do you go to?