Bitcoin Forum

Hello,

I'm just starting to read about BitCoin.

I have 45 pc's running 24/7, all connected to the internet. They are used for automation processes, and I access most of them using remote-access software.
- They're all running Windows XP (and need to remain that way)
- Most of them are intel p4's running at 2.8 ghz.
- Some of them have video cards installed, but nothing newer than 3 years old.

I've read that CPU mining is no longer profitable.... but I'm searching for a way to monetize the spare CPU time.

Any thoughts?

Forget it.  A 2.8 GHz Pentium 4 will only achieve around 1.12 million hashes per second (https://en.bitcoin.it/wiki/Mining_hardware_comparison).  All 45 computers, together, will be around 50 million per second.  You're not using spare CPU time; you'll instead be running all of those computers at full power 24/7, which is roughly an extra 70 watts each (http://img.tomshardware.com/us/2007/12/28/intel_cpu_power_consumption/image019.png).  So 3150 watts to produce 50 million hashes per second.

At the current bitcoin difficulty, it would take you around 12 weeks to generate 50 bitcoins (and that's assuming difficulty doesn't increase, which is unlikely).  12 weeks * 3150 watts = 6300 kilowatt hours of electicity.  At average US residential rates (~$0.11/kilowatt hour), that's around $700 of electricity to generate 50 bitcoins which may be worth roughly $40.  (Plus don't forget about the added wear and tear on the computers and the extra heat they'll be generating, and all of the fans that will be running at full speed all the time.)

By comparison, a single 5970 video card will use 300 watts to generate roughly 600 million hashes per second.  That is 12 times faster with 10.5 times less power, or 126 times more efficient.

So ... no.  :)

He did NOT ask what would be better
he stated he has 45 machines that already run 24/7   
Guess YOU CAN't read (or is the problem comprehension)

I'd suggest slush's pool with puddinpops rpc miner on each machine

Huh?  Looks like you're the one who can't read.

There's a difference between a computer being powered on with its CPU idle and a computer powered on with its CPU at 100% usage. It's wise not to be a dickhead when it's you that has an issue with reading comprehension.

a single GPU would be much more efficient than this old CPU array :)

maybe you should get some cheap video-cards to plug into those machines,
a single HD5570 would gain you as much hashes/s as your whole cluster at an equal power-cost of 1 CPU at 100%,
45 of them and you got a nice and cheap mining-farm.

And just what did I miss
he stated that those 45 machines already run 24/7

but  you  all insist  ... would be better .... spend on cards ...
I don't think that was his question

Yes putting a gpu in each machine would earn more
but it will take a yr to PAY for those gpu's

since he's already paying the power bill for 45 computers
what's so hard to comprehend

He's already paying the power bill for 45 computers idling - there's a difference between the power bill for 45 computers each idling on ~4% CPU, and 45 computers maxing out their CPUs at 100%:

that's untrue,
at current difficulty and market-prices it would take just about 3months to pay the 50bucks for a HD5570,
so in about 4-5months you'd be in profit.

running 45CPUs at 100% probably won't gain you any profit ever.

Guess you get better prices than  most

with 45 he'll probably see .5 or better bit coins per day
I see about .1 per day with 11 part time cpu only machines
and those machines aren't the fastest
and only another .1 from my gpu

Yes you use some more power with the cpu @ 100% but not that much
you may as well make the thing do something

"Not that much". According to Tom's Hardware (linked to twice above) it ranges from around 55W for a low-end CPU to 99W. 55W multiplied by 45 computers is 2475W. That's the equivalent of running 2 and a half "bar heaters". If I did that 24 hours a day I'd be looking for a lot more that 0.5 BTC a day to cover the increased electricity bill. You may as well save the money and buy bitcoins instead.

You can find the TDP here: Wiki http://en.wikipedia.org/wiki/List_of_Intel_Pentium_4_microprocessors
it depends on the gate width of the OPs cpu's what the tdp is

estimates are bs  what his Actual power costs are speculation
What you pay for electricity my not be what he pays
its all speculation

and just WTF is a BAR heater ?? like that means somthing

Sure, estimates are bullshit. I'm assuming low wattage and high BTC generation, and using really out-of-date - and low - costs per kW/hr. And there's still no way I can make it cost effective. Don't believe me? Do the sums yourself. Take the TDP for your chosen processor, divide by two to give the difference between idling and 100%. Now multiply it by 45 computers. That's your W/hr figure. Divide by 1000 to convert to kW/hrs. Now check an electricity bill and see how much they charge per kW/hr. Multiply the kW/hrs by the cost per kW/hr. That's the extra electricity cost that needs to be covered by - by your estimate - 0.5 BTC per day. I've seen a lot of kW/hr rates quoted here by various forum regulars, and none of them come close to making this practical. You'd need free electricity like solar or wind, and even then you'd need to factor in amortisation of capital costs (including replacing CPUs etc more frequently, because they're being run hot much more than usual).

Edit: "bar heater": Google is your friend (http://www.google.com/search?q=bar+heater&hl=en&pws=0&prmd=ivns&source=lnms&tbm=isch&ei=wB2qTZ-lKpKs8QO56ZS5Ag&sa=X&oi=mode_link&ct=mode&cd=2&ved=0CBAQ_AUoAQ&biw=1400&bih=760).

buy 45 * HD5770

p.s. I hope you have spare pci-e ...