Larry's Rule

[VirtualLarry]

When it costs more in electricity to power the CPU for a month, than what it's worth on eBay, then it's time to scrap it.

That is "Larry's Rule".

 

[petrusbroder]

Yes, that is a nice rule - I'll adapt it at once!

 

[deerslayer]

So what is the CPU cutoff for this rule currently?

 

[sangyup81]

A 100 watt CPU for someone that pays 20 cents per kwh would cost $14.40 to power for a month. Am I doing this calculation right?

 

[VirtualLarry]

It was prompted by this thread, someone was going to resurrect a Pentium D 805, which goes for as low as $7 on ebay shipped.

http://forums.anandtech.com/showthread.php?t=2390185

 

[TennesseeTony]

It was prompted by this thread, someone was going to resurrect a Pentium D 805, which goes for as low as $7 on ebay shipped.

http://forums.anandtech.com/showthread.php?t=2390185

One thing to add though, don't discount the fact that if you're primarily a GPU cruncher, those old machines are a cheap way to add another card or 2, 3, 4.

 

[VirtualLarry]

I'm re-visiting this, in light of the E8400 situation on ebay. I guess that you can find them for $6-8 shipped.

http://energyusecalculator.com/electricity_computer.htm

24/7 usage, @ 60W, and 0.15cents/KWh, is roughly $6-7/mo in electricity. Which would seem like the E8400 is right at the edge of the cutoff for "Larry's Rule".

Can I get a general consensus from the DC crowd about this? Should E8400 CPUs be scrapped for DC? It seemed obvious, in the case of a Pentium D, but it's less obvious in the case of an E8400.

Then again, the newer Haswell Pentium chips will crunch just as well on less power, so maybe the rule still makes sense.

Looking for feedback.

Edit: For an additional datapoint, consider the A4-6300. Ignoring the GPU compute ability of this APU for the moment, it seems to cost more than the E8400, but performs around E5200 level, according to CPU World's benchmarks. Also, I measured mine taking 71W max, with a not-very-efficient PSU that came with the case.

So it would seem to me to be silly, to consider the A4-6300 as DC-worthy, but not the E8400. Although, there is the IGP to consider too, I suppose.

 

[TennesseeTony]

Wouldn't you have to count the cost of the entire platform (motherboard too, as it is dated and specific to the chip in question)?

If so your ebay selling price would be much higher, making this combo a keeper.


EDIT: And the low price of the E8400 is due to the commonality. You can't dismiss the fact that it's still a respectable platform just because it's as common as rain on your day off.

But, you may want to analyze the output per watt, and see if a newer system might eventually pay for itself by replacing multiple older systems. That's how I justified BumbleBee and WUSS, The Consortium will soon be cut back to nearly nothing.

 

[Assimilator1]

I'm still using my Q9550 , although its 4 cores, high o/c & higher value than an E8400 make it more worthwhile .
The i7 upgrade has been delayed again, at least 2 weeks, & maybe more if the mbrd is no good .

 

[petrusbroder]

Larry's rule is applicable also to GPUs ...
Two of my GPUs (Nvidia 560Ti) quit on my due to the fans failing. Replacing the GPUs would be more costly than I want to. Getting an equivalent card on eBay would cost more than the power it uses ...
So I dismantled four "old" CPU-coolers (I always use after market coolers, not the ones coming with the CPU), attached the fans to the GPUs and ...
With the original fans the temps were approx 85ºC @ 100%load. With the CPU fans the temps @100% load with the same kind of WUs is 65ºC. OC-ing by 21% the GPUs rises the temp to 89ºC and the speed by 15-20%.
The backside of this? Noise ... but the computers are in the basement and are heating that part of the house, and soon the rest too ...