Can you guys check this electricity comparison over for me?

[DrPop]

Alright, so I just did the math - running the highest end AMD rig from BikerMatt for the Hydra here - and if I were to swap it out for a Sandy Bridge setup, this is what I find:
The difference in TDP is 30W - (125W for AMD X6 and 95W for i7).
That 30W equates to roughly 25.2KW over the course of a month at 24/7 operation.

Now, taking good hard look at my electric bill, I happen to notice that most of the "fees" I pay for my office are "built in" transmission, delivery, blah, blah charges - like half of them don't even matter how much juice I'm sucking down, they are just going to be high because it's a business. OK, big deal, right? So I did the math on the part of my bill that would actually change, and ...
I get a whopping like $4! That's it. Let's give it the benefit of the doubt and say I screwed up somewhere and it would be $5 per month savings with the i7 CPU.
That still makes it only $60 per year power savings at 24/7 usage. Verdict: it would take a looooong time to save the cost of one of those things in power savings. Not really sure it's worth it, unless the points are just so good with it over the AMD X6 cpus?

Clearly I was expecting a bigger difference in power bill savings, and maybe it would be for someone on a residential line, I don't know. Anyway, just thought I'd share...back to debating about GPUs now.:rolleyes:

[spingadus]

Sounds about right.

30 W = .03 kW

.03 kW over 30 days = .03 kW * 720 hrs = 21.6 kWh

21.6 kWh at 32 cents per kWh = 21.6 * .32 = $6.91 (Assuming a super high rate of 32 cents/kWh).


But what is the actual power usage difference instead of TDP?

[John P. Myers]

Alright, so I just did the math - running the highest end AMD rig from BikerMatt for the Hydra here - and if I were to swap it out for a Sandy Bridge setup, this is what I find:
The difference in TDP is 30W - (125W for AMD X6 and 95W for i7).
That 30W equates to roughly 25.2KW over the course of a month at 24/7 operation.



bleh nvm. spingadus beat me :)

The power savings are great when you don't have a system, then you make one. But swapping out a system to save power isn't feasible unless you're doing a large upgrade at the same time.

[John P. Myers]

However, i can add this:

Intel Z68 chipset 6.1W
AMD 890FX chipset: 18W

so there you save another 8.568 kWh/month on top of the 21.6 kWh from the CPU alone. Still not enough to justify it? Didn't think so :p


But what is the actual power usage difference instead of TDP?

TDP generally is the actual amount the chip uses (at stock speeds). And it is in the manufacturers best interest that it is, because computer/heatsink makers use this number to design the heatsinks for the chips. If they under-value this number, then heatsinks fail and someone gets embarrassed. If they over-value it, then they just look really inefficient. It is worth noting though that this number is not exact, but really close.

[DrPop]

Holy smokes! Intel's chipset is 300% more efficient? What the heck did they do so different? Not that it's enough to make worth changing over electric cost, but anyone out there buying new right now. . .

[Fire$torm]

However, i can add this:

Intel Z68 chipset 6.1W
AMD 890FX chipset: 18W

so there you save another 8.568 kWh/month on top of the 21.6 kWh from the CPU alone. Still not enough to justify it? Didn't think so :p


But what is the actual power usage difference instead of TDP?


TDP generally is the actual amount the chip uses (at stock speeds). And it is in the manufacturers best interest that it is, because computer/heatsink makers use this number to design the heatsinks for the chips. If they under-value this number, then heatsinks fail and someone gets embarrassed. If they over-value it, then they just look really inefficient. It is worth noting though that this number is not exact, but really close.

JPM, I hope you are referring to heat energy and not P=I*E. TDP = Thermal Design Point / Thermal Design power and equates to heat generation. CPUs are mostly solid-state transistors, and transistors are at best 50% efficient in converting current( Current = Amps = Voltage / Resistance) into useful work in the "On State". The rest of the current is dissipated as heat.

Even Wikipedia misses the mark on TDP (Link (http://en.wikipedia.org/wiki/Thermal_design_power)), that article keeps using the term power incorrectly as it never properly distinguishes the definitions as used.

Wikipedia:
Heat (Heat Energy): http://en.wikipedia.org/wiki/Heat_energy#.22Thermal_energy.22
Heat (Heat Energy) - Notation and units: http://en.wikipedia.org/wiki/Heat_energy#Notation_and_units
Heat (Heat Energy) - "Thermal energy": http://en.wikipedia.org/wiki/Heat_energy#.22Thermal_energy.22

Ohm's Law: http://en.wikipedia.org/wiki/Ohm%27s_law
Ampee: http://en.wikipedia.org/wiki/Ampere
Watt: http://en.wikipedia.org/wiki/Watt

[Bryan]

According to the Sandy Bridge datasheet, if you are running at 95W TDP the power consumption is 170W. VID @ 1.52V and Icc @ 112A.

95W TDP would require that ALL features, ports, etc are active at the same time and pushed to the max. TDP is the amount of heat energy that must be removed from the device or else it self destructs ... as in thermal runaway/meltdown.

[John P. Myers]

@Bryan well i should think so. 1.52V is far above spec. and 112A? hmmm

http://valid.canardpc.com/cache/banner/1804313.png (http://valid.canardpc.com/show_oc.php?id=1804313)
Sandy Bridge OC'd by 1GHz and still far under that voltage.

@F$: i was thinking of P=CV^2F, though to solve for P, i can never find a value for C (capacitance) so i usually end up digging for P and solving for C...which doesn't really help...at all lol

[Bryan]

@JPM, yep 1.52V. Look at the spec table (1st line/last line) in the 2nd generation family datasheet .... page 80

http://www.intel.com/content/www/us/en/processors/core/2nd-gen-core-desktop-vol-1-datasheet.html

Each processor is programmed, at manufacture, with the maximum value for THAT processor for voltage. It is the VID and will be up to a max of 1.52V. Two processors of the same type and running at the same freq. can have different VID values.

I think the 112A is max. current with 85A being the sustained value. The graphics core pulls a max of 35A with 25A being the sustained value.

Somewhere Intel has a "load line" for the processors but I haven't been able to find it. It is mentioned in the datasheet.