Last summer I was in the top tier of electricity usage, which at the rates in central California means I was paying $0.40/kWh on the last couple kWh of electricity I used.  I've made a few changes to my house this year, but I'm sure I'll be hugging that line of top tier costs again, even without counting the 3 mining rigs I'm now running.

I've prepared my rigs based on an estimated cost of $0.40 USD per kWh, and only about 35% of the BTC generated (at $1.1/BTC) needs to be allocated towards electricity.  The rigs should pay themselves off within 4 months even assuming a worst case scenario of summer electricity rates.

Update on my hashing capacity:

Gaming Rig (1x 5970) - 600 mhash/sec
Mining Rig #1 (2x 5870) - 760 mHash/sec
Mining Rig #2 (2x 5870) - 750 mHash/sec

Built Mining Rig 1 on Monday this week, and it went so well that I customized a cheaper version of the internal components/case for Mining Rig #2.  If it weren't for having to pay sales tax on a few parts, the rig would've only cost me $1 per mHash/sec capacity.

I'd recommend checking your power consumption.  I lose about 20 mH/sec underclocking my memory, but it is more profitable (mHash/kWh).

1 gHash/sec roughly in my current setups.  1.35 gHash/sec this afternoon with my next 5870.  Considering building another new rig for a second pair of 5870s.  It seems that it's cheaper to build 2 rigs with 2 5870s each rather than a single quad 5870 setup.  The motherboard, case, and power supply for a quad 5870 setup are pretty pricey, not to mention possible cooling issues.

GPU ran all night hashing away at 1020 core and 600 memory, maintaining the 385 mHash/sec, and only hitting 68C without fail.

I actually tried restoring the memory to the 1200 original clock speed, and it did increase my mHash/sec to 398, but the power consumption increase reduced the mHash/watt ratio.  After work tonight I'll start working on different memory clock speeds to find the sweet spot for mHash/watt.

My second 5870 gets delivered today as well, hopefully I get one that performs like the first!

Yeah, I really just started the heavier OC'ing today, last night I ran it at 900 and all went well.  When I got home from work I pushed it to 975 just to be risky and saw the temps barely rise and power consumption only go up maybe 8 or 9 watts.  After a few hours at that I've put it at 1000 and will let it run 12-24 hours at that speed before I try going any higher.

AMD Sempron 140 with the 2nd core unlocked.
2 solid state drives (1x Kingston 16 gB, 1x OCZ 60 gB)
4x case fans (3 230mm, 1x 140mm)
1000 watt PSU (Cooler Master Silent Pro, got such a massive one in case it ever expanded into dual 6990s)
4x GB RAM (4x 1 gig).

I'm planning on using the rest of the build for a medium sized web server while the GPUs do their mining, thus the double SSDs (boot drive & mysql/storage drive), RAM, and unlocked 2nd core of the processor.

The whole computer is consuming 272 watts right now with the card at 1000 mhz.  I'll be able to give an "isolated" card power consumption this weekend when I get the 2nd 5870, by taking the total PC consumption less the 272 I already know it consumes.

It's running Ubuntu 10.10 desktop install.  ATI Stream SDK 2.1.  The ATI driver is Catalyst 11.3.

Just wanted to share the results of my new mining rig.  Original plan was a 6990, but TigerDirect FUBAR'd that order.  I ended up getting a 5870 delivered before fixing the 6990 order issue, and I'm amazed at how well its performing.

GPU Overclocked to 950 (stock voltage).
Memory underclocked to 600 (haven't been able to go under that inside linux?).
Fans running at ~50% (2400-2500 RPM out of 5100 according to AMDOverdriveCtrl).
Runs at a steady 65-67C.

That's producing a 362-364 mhash/sec rate of mining (m0mchil's poclbm), which is higher than any of the wiki entries for a 5870.  I'm going to slowly drive up the GPU clock rate every few hours to find the sweet spot for power consumption, temperature, and mining rate.  So far the 950 clock rate is a better mhash/watt ratio than 850, 900, and 925.

Has anyone else been pulling these numbers (or better) on a 5870 with just stock cooling?  I'm curious why the wiki numbers are quite a bit less.

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Update 4/25/11:  I switched over to the Phoenix miner 1.1, and now run at 421-423 mHash/sec on all of my 5870s.  Clock settings are 975/300, using 0.950 voltage.  They're running cooler, sucking less power, and running significantly faster with Phoenix!

Have you tried plugging another monitor into the second card?  You may need to get a DVI->VGA Dummy Plug (search for VGA Dummy Plug for a guide on how to make one) to plug into the second card.

I have not yet been able to create an interface on my store for automated BitCoin transactions, but I will accept private orders!  My prices are always highly competitive (almost always lower) than the buy it now prices you'll find on eBay.

I have about 500 games available on my store right now, and I'm adding 100-300 every weekend.  As of this post, the exchange rate is 1:1, but it will vary based on the Mt Gox exchange rate day to day.  Do not bother making offers that low ball the USD price (ie: 10 bitcoins for a $12 USD game).

Would love a copy of that, but at that price I don't think I'd ever break even with the cost of 6990s and the insane cost of electricity in California.  At least not without a six figure investment in hardware capacity.

Alright, so it looks like the best way to utilize the 3 cards would be:

Mining Rig: 6990
Gaming Rig: 5970 mining when not in use.  5870 added to system, and mining 24/7.

So since the 6990 might not be ready for full duty mining yet, should I swap my 5970 (currently in my gaming rig) with the 6990, and then plug in the 5970 and 5870 into my mining rig?

Yeah, I'm interested in seeing the temperature interaction between the two cards.  I'm using a Cooler Master HAF 932 for the rig, which in my experience with gaming rigs is able to very easily run multiple hot GPUs without much issue.

When building a computer specifically for mining BitCoins, with ATI/AMD cards, is it neccessary to match the cards up like you would in a gaming machine, or can I simply plug in whatever card I have available at the time?

Right now I have a 6990 on the way, and I already have a 5970.  Can I just plug in those two cards without any special setup?  Additionally, could I add a 5870 to the mix as long as the motherboard / PSU can support all 3?

I'm looking into setting up a BitCoin checkout in my online video game store, started in January (http://www.eleuthria.com).  Trying to determine the best way to automate the process and hopefully get it implemented near the end of the month.

I'm also looking into commercializing my store's engine later this year, since I have some very unique features thanks to coding it from scratch.  The store is integrated with eBay and soon Amazon, so a store can easily sell on all 3 websites while keeping a single central inventory which can remove products/quantity counts from each site as they sell on the others.  If I do that, I will definitely look into including BitCoin as one of the checkout options in the default build.

So since it sounds like Linux is currently out of the question (or at least not optimal), which version of Windows should I use (if it matters)?

Can you elaborate on "tweaking every little aspect"?

I know I'm definitely going to underclock the memory speed to suppress the power drain as much as possible, and play with the core speed to find a sweet spot for Mhash/W vs Mhash/sec.

I'm building a rig with the immediate goal of running just a single 6990, and then adding on another 6990 in a month or two.

What will give me the best results for Mhash/sec currently, Linux or Windows?  Which distro of Linux or version of Windows should I load onto it?


Building it with the following:
  Case: Cooler Master HAF 932
  Motherboard: MSI 870-G45 AMD
  CPU: AMD Sempron 140
  RAM: 2 gigs
  HD: 16 gigabyte solid state drive
  Power Supply: 1000 watt