Congratulations! Does the lender want to remain anonymous? There aren't that many people around here that can handle loans that big.

Also, do you plan to sell the coins on MtGox or arrange a private sale without moving the market? When trading large amounts, I typically try to find someone in #bitcoin-otc, first because it can potentially be slippage-free, but also because it's just a more subtle way of doing things (and I love to be subtle). Since I'm overall long bitcoins, I'd prefer not to do much to lower the MtGox price where possible

No, you could get totally screwed going long 10:1 if the price drops even a bit before it skyrockets. Even 2:1 isn't what you want, plus that would require more hedging capital. You need an option to buy coins at or near the current price in 5 years time. That's not going to be easy to get because anyone who will promise do that for you won't hold them or be able to afford coins if they skyrocket or else they are holding them because they expect them to go way up and will charge you a lot.

For your case I would borrow dollars with an agreement that you can pay them back with bitcoins at the market rate. I don't think anything else is going to match up perfectly with what you want.

How about getting a gas dryer??? The outlet & all its glory will be yours

Tell her the outlet is yours now then direct all the heat from the gpus thru ducting to a drying rack.  Hang the clothes on the rack, sell the dryer.

Short answer: Yes, slightly better performance is possible.

Long answer: You can expect a little more performance, but unless there's a detail I'm not aware of there is really not much left to gain (1-2% ideally). Let me explain why.

To the best of my knowledge, the closest estimate of the number of mathematical operations required to compute 1 hash is ~3375 (according to Phateus). And if we consider an ideally efficient processor to be one that computes mathematical operations at a rate of one operation per cycle, then hashing would take ~3375 cycles on this ideally efficient processor.

Now lets take a look at what kind of performance we can measure with today's kernels. The 7970 has 2048 stream processors and a stock frequency of 925Mhz, and with the best known kernels it is computing 550MH/s. Knowing this, we can measure the average number of cycles it is taking each stream processor to compute one hash using the following equation:


Now if we consider that each stream processor at best can perform one ALU instruction per cycle, then the 7970 is extremely efficient (in cycles per hash) since this 3444 cycle measurement is reaaaallly close to the ideal value of 3375 cycles at one instruction per cycle. This is only a ~2% difference off of ideal and might even be due to measurement error. Its so efficient that unless there is a breakthrough that reduces the amount of operations required per hash, or there's some new GCN instruction that I'm unaware of that allows the GPU to compute several steps of the hashing function in one cycle, or kernels are modified to start taking advantage of fixed-function hardware somehow, then to the best of my knowledge ~550MH/s at stock clocks is pretty much all we're ever going to get.

To give you an idea how efficient the 7970 is at computing hashes we can compare its efficiency (in cycles per hash) with a 6970, which has 1536 stream processors and a stock frequency of 880MHz for the highest reported hashrate of 370MH/s at that frequency (from the mining hardware comparison chart):


At an estimate of 3653 cycles, a 6970 stream processor takes ~6% more cycles per hash than a 7970 stream processor at the same frequency, and ~8% more than the ideal 1 instruction per cycle processor.

Now lets compare to a 5870 which has a highest reported hash rate of 379MH/s with its 1600 stream processors and a stock speed of 850MHz:


This makes the 5870 roughly 2% more efficient (in cycles per hash) than the 6970, but it still uses ~4% more cycles per hash than the 7970, and ~6% more than the ideal processor. So we can conclude that ATI's GCN is already making ~98% efficient use of its stream processors for hashing, which is more than the VLIW4 and VLIW5 of its previous two generations and close to the ideal. This more efficient stream processor usage along with the increased number of stream processors and higher stock frequency explains the increased hashing performance when compared to the previous generations of GPUs.

Disclaimer: I'm not a GPU programming expert (yet) so please take my answer with a grain a salt. But for what its worth, I develop HPC software for a living that solves problems running on thousands of nodes in parallel.

I think I did pretty well on it.  My goal was lowish power at wall / low initial investment.   I bought lots of parts used, or discount/rebate.  Let me know what you guys think.


Parts/prices include shipping.
$40 CPU/Motherboard/Ram: ECS 945GCD-M(1.0) Intel Atom 330

• Seller also included 2 GB DDR2
• Has 1x PciE 16x slot, 1 PciE Slot
• Pulls 30 watts at wall idle, no video card

$40 GPU1: 5770, XFX 577A-ZNFC
*Purchased used from a friend who was getting rid of his crossfire setup

$40 GPU2: 5770, XFX 577X-ZNFC
*Purchased used from a friend who was getting rid of his crossfire setup

$13.99 PSU: Corsair CX 430
*Bought ~6 months ago from newegg after rebate. I had a few extra molex to PCIE adaptors for the second card.

$8.98 Pair of 16x to 1x PCIE converters from Amazon, only ended up needing one of them.

Free Case, old beige box mATX compatible, cut a few holes in it to add fans.

$6 OS: Linux running on a 8 GB Flash Drive



Total: Cost $150.97
MHash: ~380

I'm running the pair of 5770s at 900MHz @ 1.125v.  Full load power draw is ~190w at wall.  I hoping tweak it farther to bring the MHash up to 400ish at similar power draw. 

Cost at current speed works out to: $2.53 per MHash purchase price. Running cost is right at 2 watts per MHash.

Think I did allright?

My 6870 works great at 1000 core, 300 memory for ~318-320 MHash/s. Actually getting down to 300MHz is a chore, I have to set it to 300 in Afterburner and then manually set the L1 to 300 using clocktweak. Underclocking the memory makes a pretty substantial drop in power though.

If he's got a fancy front-loader that's a high efficiency model, it's actually pretty likely that it's running a brushless DC or PMAC motor. The nicer white goods have been moving in that direction for awhile, I don't think many new front loaders have been made with shaded pole motors.

What's the model of the dryer, yochdog?

There might be - but Code requires a dedicated circuit for a reason.

See if you can find the nameplate rating of the device, just to be sure of the wattage.
Most dryers use a capacitor-start motor that runs at a constant speed - such motors make all kind of nasty electrical anomalies when they start, not to mention a large additional power draw. The motor might take up to 400% of its rating during the few seconds that it is starting, and that would trip the breaker if you removed the additional overhead allowance that is already built into the circuit by running some rigs on it. Now obviously, the motor isn't the main load - the main load is the resistive heater inside, which switches on and off to maintain different temperatures.

If we assumed that a 40 amp 220v circuit could supply approximately 7KW of power (after derating), and if we assumed that the dryer was 2KW like you mentioned, you should also assume spikes of up to 3KW during the motor start phase for a few seconds. This leaves you with potentially 4KW of "spare" power. You might be able to open the power outlet and add some #8 wire to extend the branch circuit to another plug. However if you do this, you really need to get a PDU with its own circuit breakers built in, otherwise you risk fire from under-rated wiring. I wouldn't want to suggest more than 20 amps of 220v coming off of the PDU in this case, since it isn't dedicated.

Finally, if you do this, make sure you have absolutely top-shelf PSUs. Since they will be so electrically close to the nasty power spikes caused by the motor starting, they will be more susceptible to failure.

20 amps at 220v should allow you to run several rigs. Good luck, and don't let the inspector see it!

LOL, switch back and forth... Do you know how much power that dryer uses?  You might be able to run maybe 1 card with it running.

Are you still looking for a partner?

Your argument is invalid because 3.74 Mh/J is also influenced by unknown variables, such as the efficiency of power supplies which varies with load: http://www.anandtech.com/show/2624/3

Here is a thought experiment: yochdog's load/idle power draw is 512/154 Watt. He replaces his power supply with one that is just as efficient at high loads, but more efficient at low loads, changing his measuremnts to 512/130 Watt. Suddenly his mining efficiency went down from 1340/(512-154) = 3.74 Mh/J to 1340/(512-130) = 3.51 Mh/J ! Explain to me why using a formula in which efficiency becomes worse when using better hardware components is useful?

Of course, if everybody had clamp meters, the ultimate way to measure the efficiency of a card would be to measure current at the PCIe power connectors and PCIe slot, like I demonstrated a while ago: http://blog.zorinaq.com/?e=42

I may be interested in the 30 day, but we need to talk some numbers over PM