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PSU power consumption?

Last response: in Graphics & Displays
May 25, 2009 3:03:12 AM

Hi all,

Quick question about PSUs, please.. I have a OCZ 850watt PSU and plan to get 2x HD4890s in CrossFire. I am concious of power consumption of my PC because I like to limit my power bills as much as possible and, obviouly, don't need the power of 2x HD4890s for 'daily' usage. Can I easily switch off one of the 4890s (disable the PCIe or something) for daily usage and just run the single GPU card?

Also, appologies if this question should reside in the Graphics and Display forum (if so, please move it). I wasn't sure where it was best suited.

Any tips on limiting power consumption for high-demand systems?

Cheers :-)


More about : psu power consumption

May 25, 2009 10:35:06 AM

AFAIK, you can't turn it off while you're running your OS. Though I do know if your motherboard allows it, you can turn it off one card or even both (switching you back to integrated graphics) in its menu. Unfortunately this means restarting your system.
May 25, 2009 11:45:32 AM

You could always build a second low-power system for your daily usage and save the beast for gaming.
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a b U Graphics card
a c 144 ) Power supply
May 25, 2009 11:51:02 AM

Kraynor's got it. Build a cheap little workhorse system and team it with an inexpensive 2 port KVM switch so you do not need to duplicate monitors, keyboard, and mouse.
May 25, 2009 1:56:41 PM

This topic has been moved from the section CPU & Components to section Graphic & Displays by Justinblue
a b U Graphics card
a c 139 ) Power supply
May 25, 2009 9:00:37 PM

Kraynor said:
You could always build a second low-power system for your daily usage and save the beast for gaming.
Or use a laptop computer.
a c 365 U Graphics card
a b ) Power supply
May 26, 2009 12:09:05 AM

As other have said, you could build a separate low power system for everyday use and buy a KVM switch to share the same keyboard mouse and monitor. However, going this route, you must take into consideration the cost of a new system and how much electricity costs you expect to save doing so.

For example, assume a low power system will cost $300. Let's say the wattage difference of both PC while doing "low power stuff" is 150w and you spend 15 hours a week (or 60 hours per month) doing "low power stuff". Last time I check the national average cost of electricity was $0.11 per KWH (I wish I was paying the national average).

Based on the above, you will save 9KW per month using a lower power system (150w x 60 hour), and that works out to a savings of $0.99 per month (9KW x $0.11). Let's round that up to $1 per month, $12 per year of electricity savings. To break even you would need keep switching between both systems for 25 years ($300 / $12 per year).

Having two systems to for "cost savings" does not work.

Ways to save on electricity:
- The single most important thing you can do to reduce power consumption is to buy a PSU that is 80Plus certified. That way less electricity from the wall is wasted as heat and noise.

- Buy an efficient CPU, the smaller the die size, the less electricity the CPU will consume compared to a similar larger die size CPU. Example, Q9450 uses 55ms tech, Q6600 uses 65ms tech, the Q9450 is a little more powerful (from what I remember) and it consumes slightly less power.

- Buy power efficient hard drives like the "GREEN" WD HDDs. They basically run at 5400RPMs compared to higher performing 7200RPM HHDs, but you save some electricity while idling and during usage.

- Do not overclock anything. Overclocking will give you better performance, but will also cause the component to draw more electricity.

- Do not use a sound card, use integrated audio. This will save you a few watts.

- Last suggestion (since you want to play games), drop the 2nd HD 4890, or consider XFiring two HD 4770. A single HD 4770 uses 50w of power compared to 130w of a single HD 4890. That means in an XFire setup you will save about 160w of power, the trade off is lower performance.
May 26, 2009 5:09:46 AM

Thanks to you all for your input.

Regarding a second PC - ya'll don't know how hard it was to convince my better half that I even needed 1 PC, let alone a second one! LOL. She'll hit the roof if I have a second 'box' right after buying this one!!! Plus, I think jaguarskx has a point about the power savings VS the cost of the second PC.

I do own a notebook but planned to use this only as a media centre (docked near my TV) and didn't want to be unplugging it and moving it between the TV stand and my desk etc. That said, it's a possibility. My woman also has a notebook which I can use for daily stuff so that's probably my best option..? PC for gaming and 'her' notebook for web surfing / documents etc. That said, she is studying at college so I'll have limited access to her notebook.

I think the answer is to go with just 1x HD4890 for now and see if it gives me the gaming performance I was wanting. Afterall, it's no hassle to order a second 4890 later on (the prices on 4800 series will likely drop quite a lot once the 4900 range is released).

Is the i7 920 an efficient CPU? That's what I'm going with.

Thanks again,

a b U Graphics card
a c 139 ) Power supply
May 26, 2009 1:58:19 PM

doakwolf said:
Is the i7 920 an efficient CPU? That's what I'm going with.
Not so much.
CPU power comparisons
a b U Graphics card
a b ) Power supply
May 26, 2009 6:41:33 PM

Also, as much as I hate to admit it, Nvidia kills ATI on idle power consumption (what the card will be doing while surfing the web). If power is a serious concern, check the idle power consumption of the cards you are looking at.
May 27, 2009 1:48:07 AM

WR2 said:
Not so much.
CPU power comparisons

Ehh :na: 

Ah well.

Thanks again to you all.

Oh, I have been considering NVidia for that reason, EXT64. I still might consider a GTX275 instead of the 4890.
a b U Graphics card
a b ) Power supply
May 27, 2009 2:38:42 AM

Yeah, they are both solid cards. So see which play games you like better and which gets better idle power consumption (check major reviews, most usually include that). In the past NVidia was much better then ATI, but I know the 4890 has much more aggressive downclocking then past 4000 cards (not sure if it helps enough though).