Bitcoin Forum

Is there a good chance that dropping $400-500 on dual 6950's would pay themselves off within a month or two?
paying off the hardware I think would be all really *require*, and I think this is kind of a fun experiment to see where it leads.

i'm guessing that 2x 6950's would net me around 675-700 mhash/sec  (someone please correct me on this if wrong)

factor in a.) expenses b.) vs profit..

as far as b is concerned, at ~700mhash/s you'd probably earn under 20 btc a month (i'm completely estimating). assuming exchange rates hover around 20, that'd be approx $400 a month

so the question goes back to a.), is your electricity bill going to be under 400 a month with the extra use of electricity/cooling/etc (not factoring the initial expense of card purchase/install/time spent installing it).

You would be correct. But the rate in which you earn bitcoin will change so It will take longer than you think to pay the cards off.

also saw this on another thread, a caulcator to figure how much power your system is going to use..

look at your electricity bill and figure out how much they charge you..

then look at mining pool stats and estimate how much those 700mh/s earn and extrapolate it over a months worth (or whatever time frame you want).

would help if i post the link to the calculator i was talking of:

http://extreme.outervision.com/psucalculatorlite.jsp

(yeah i know i could edit my previous post but, i really need the post count so i can get out of this newbie-dom-hell so i protest conserving post-creation)

i think i originally did my estimates based on 1.2mil difficulty, which is probably a pretty sure thing before the month is out...
not really sure if there's a solid way to project what will happen in july.. I mean.. even if I was only returning $100-$200/mo it would eventually pay itself off

oh.. and we have really cheep power here... $0.08 /kWh

Well, depending on how fast the difficulty ramps up, it may take you awhile to break even. At least 2 months or more.

When you're discussing 6950's, make sure you clarify if you plan on using reference or non-reference cards.  The former have a bios selector switch allowing you to either switch to the 6970 bios or simply unlock the dormant shaders, both of which offers a performance increase.  The non-reference (1gb) cards do not offer this feature.

I've spent the last week optimizing my 6950's for ideal performance, and after separating them in my case (leaving a double-bay PCIe slot empty) I've been able to achieve a maximum hash rate of 660Mhash/s while still keeping temperatures in check.

My setup:

Windows 7 64-bit
GUIMiner running OpenCL miners
Dual non-reference 6950's clocked as follows:
1150mV, 910MHz Core Clock, 650MHz Mem Clock, 98% utilization at 79 degrees C for each card.
Flags: -f128 on both cards.
TONS of airflow in the case.

Honestly, I think expecting anything above 650Mhashs on a set of non-reference cards is dreaming, though you could probably achieve upwards of 800Mhash on reference 6950's with unlocked shaders and a substantial OC.

is there any online source of historical difficulty levels (so we may see how they've changed over time).

6950s are currently not terribly cost effective for the hash rate they produce

i still don't get why people buy purpose-built gpu's just for mining.. i mean if you're in the market for a new gpu to game or whatever (i think i outgrew gaming) then ok i see.. but to buy gpu's just to mine? seems like a waste of time, you could easily just exchange your $$ for bitcoins with a lot less trouble a far more immediately, unless you have some grandiose plan to get rich off mining (i have a bridge i'll sell you too i heard it'll go up in value also).

but seriously, realisticly how high will bit coins go though? they hit just under $32 per bitcoin, yes i know there'll be a finite supply one day but that's still decades away..