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View Full Version : Calculation power useage (new video, new psu?)


Lars-Erik
01-14-07, 02:53 PM
Anyoneout there have a clue about calculation power consumption?

Before I buy a new PSU I had a look at my old one.

It's a Enermax 350W and the label states these specs:

Enermax EG365P-VE

+3.3V +5V +12V -5V -12V +5VSb +3.3&5V Total
32A 32A 26A 1A 1A 2,2A 185W 350W

105W 160W 312W 5W 12W 11W 185W 350W

The last line is my calculated Watts for the lines,
strange that the sum of the individual lines is much
higher than the total (it's not on new PSUs). Is this
something fishy, or what does that really tell you?

As you see it has only one 12V line, and this today powers:

- Asus P4PE mainboard (with Promise S-ATA raid ctrlr)
- Intel P4 2.54 Ghz (478 socket) with stock fan
- Creative SB Live 1024 PCI sound card
- Plextor PX-716A DVD-writer
- Samsung Spinpoint 120 250GB S-ATA harddisk
- Asus V8440 Nvidia Ti-4200 video card

Now, if I replace the video card with a 7600GS
will this work, or will my PSU give up on me.

How much Amps will the other stuff in my rig use?
It's the CPU that takes most juice here, right?

Is there any tables or any experiences that would
help me calculate this? Or do I need a new PSU?

Dudes__Geof_
01-14-07, 03:04 PM
If you get a 7600GS, nothing should die, but personally I would get a 450W PSU just for a bit more 'oomph', just in case. The 7600GS is a lower end card, so I don't see that there should be any issue with the 350W. I used to run my AMD 64 3000+ overclocked, and my 6800GS with 1GB of ram with a 350W PSU without a hitch.

There should be a web-based power calculator around on the internet in a few different places if you search for it, and if I recall, a link to it has been posted on NvNews in the past as well.

I wouldn't be able to say for certain why the sum of each line comes out to more than 350W, but there is probably a good explanation and I would much rather avoid making myself sound/look stupid ;)

Edit - I think that it might be because that's the max amount of power each rail can provide to a device(s) at once, and the total is the max that the whole power supply can supply at a given time.

Lars-Erik
01-14-07, 03:09 PM
If you get a 7600GS, nothing should die, but personally I would get a 450W PSU just for a bit more 'oomph', just in case. The 7600GS is
If I'm going to buy a new PSU I want to buy one I can use in my next rig.

So then I'll go for an Enermax Liberty 500 or a Seasonic S12-600.

But I'm not sure if that is a good investment.
For all I now they might be too small in 2-3 years for a new rig.

The power-consumption for new graphic card are HUGE.
Or will there be like the "7600GS", a bit slower, less consuming variants?

Besides it worries be to put in a new PSU without -5V as the spec of my Asus P4PE says it use it (or the connector diagram), but everybody says it don't.

Dudes__Geof_
01-14-07, 03:37 PM
It shouldn't really cause a problem without a -5V rail. Only some power supplies will cause problems with certain motherboards and it's not that common. (I think Roadhog mentioned the Antec Neo PSU's with Asus motherboards don't work well together -- if at all).

A 7600GS isn't super high end to start with, so I doubt there will be a problem.. I'll see if I can find that link.

Edit - http://www.extreme.outervision.com/psucalculator.jsp

Dudes__Geof_
01-14-07, 03:48 PM
According to that, with a 7600GS, the power consumption for your computer would be less than with the TI-4200.. :|

.. And well within good range for the power supply to handle. Of course when I did it, it was rather roughly done because I don't know everything that you have connected but it came out to about 200W.

Lars-Erik
01-14-07, 07:04 PM
Found something interesting. Most versions of this PSU tested has a 16A +12V line, but apparently I'm lucky and I have a newer model of it with 26A +12V (it's even possibly to buy new today, that's strange, 4 years after :-)

The strange totals (sum of wattage beeing higher that the total) by
this table I found at http://www.enermax.com.tw/english/product_Display1.asp?PrID=29

It seems like the 3.3/5V and 12V share something inside the PSU.

EG365AX-VE(W) / EG365AX-VE(G) / EG365P-VE

+3.3V +5V +12V -5V -12V +5Vsb Total
32A 32A 26A 1A 1A 2.2A 350W
----185W---- 312W 5W 12W 11W
--------322W-------- --------28W--------- 350W

As you see from the table the 3.3/5 and 12 share 322W, but that should mean that when moving the graphics card load from 3.3/5V (with the Ti-4200) to 12V (with the 7600GS) the load is still in the same 322W (that even suggest that a 7600GT card that has the same W as the Ti4200 would work too :-)

That is if I have understood how this "sharing" of power works :-)

john19055
01-15-07, 03:52 AM
http://www.newegg.com/Product/Product.asp?Item=N82E16817163111
I would get one with enough juice incase in the future you wanted to do more upgradeing you would have the power.This one has 38amps on the 12v rail and 45amps max ,it just has one 12 rail ,but it handle my 4400+ at 2.75gig and four hardrives and four sticks of memory and two optical drived and two 7900GTX's that were overclocked.

Lars-Erik
01-15-07, 08:10 AM
> +3.3V +5V +12V -5V -12V +5Vsb Total
> 32A 32A 26A 1A 1A 2.2A 350W
> ----185W---- 312W 5W 12W 11W
> --------322W-------- --------28W--------- 350W

Just for the fun of it I hooked up a power meter between the wall outlet and the extension cord to the PC (with cable-modem, router and sub-woofer on same extension cord, so I'll have to subract for those)

Idle: 120-123W
Peak: 194W

With an effenciy factor of 80% (very optimistic for an old PSU)
that would give a max power consumption for my system of 155W.

And that's far from what the PSI is supposed to have as max
(it's not more that it could be drawn single for any line).

So if the 7600GS draws even the same (but from another line)
it would still be under HALF the max power output of the PSU

I'm more worried about the heat now. My new HDD and the CPU
generates a lot of heat when stressing the system. Today I have
a NV-silencer on my Ti-4200 card so that air is blown straight
out (and it is HOT). With a new card w/o external exhaust that
heat would have to pass the CPU and part of it the PSU on the
way out. Well, well. The Ti-4200 DID work with standard fan.