curious about the power consumption

[klayus]

I have 2 x 5870 running on a rig with the cheapest one core amd processor and 2 gb of ram and a 750W power supply.
my power panel shows that i've used 460kw of power in the last 2 months. doing some calculations that means that my rig took 314W of power for every hour it was working.
this consumption is much lower than what i anticipated. the 2 cards are overclocked to 980 core and 300 memory and they make about 420 MH/s. they were up 98% of the time in this 2 months time frame.
can this be true?

[Xephan]

I have 2 x 5870 running on a rig with the cheapest one core amd processor and 2 gb of ram and a 750W power supply.
my power panel shows that i've used 460kw of power in the last 2 months. doing some calculations that means that my rig took 314W of power for every hour it was working.
this consumption is much lower than what i anticipated. the 2 cards are overclocked to 980 core and 300 memory and they make about 420 MH/s. they were up 98% of the time in this 2 months time frame.
can this be true?

Sounds slightly on the low side, might want to get a wattmeter to confirm.

[Jack of Diamonds]

Mining is stressing on the GPU but not nearly as much as something like Furmark that would push the cards to it's absolute limits.
You aren't even utilizing the video memory at all for one.

It's very possible two 5870's would only consume 300-320W together while mining. Does sound a bit low but you could also have premium chips

[klayus]

if it is so then, before i had the 750W power supply i had a chieftec 650W supply that would stop when both cards were running. i did again some math and :
a 650W power supply with 80% efficiency gives me 520W of power available for my computer. it seemed it wasnt enough as it was shutting down the computer every time both cards started work
the 750W power supply does not have this problem!

it goes beyond my understanding what goes on with the power consumption, i'm just glad it's less than i anticipated

thanx for your help

[Xephan]

if it is so then, before i had the 750W power supply i had a chieftec 650W supply that would stop when both cards were running. i did again some math and :
a 650W power supply with 80% efficiency gives me 520W of power available for my computer. it seemed it wasnt enough as it was shutting down the computer every time both cards started work
the 750W power supply does not have this problem!

it goes beyond my understanding what goes on with the power consumption, i'm just glad it's less than i anticipated

thanx for your help

You're mistaken about the efficiency. A 650W with 80% efficiency gives you up to 650W of power, but to do so it will use up 813W measured at the wall. A 750W with 90% efficiency gives you up to 750W of power, but to do so it will use 833W. So you get 100w more power but pay bills for 20W more with a more efficient PSU.

I'm leaning towards the possibility that you're estimating your power consumption wrongly.