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So I'm a computer enthusiast and I love putting together new systems and coming up with builds. I'm just building this theoretically, not literally. Just trying to come up with the most efficient BTC monster I can. Give me your input people.

MSI 890FXA-GD70 AM3 AMD 890FX - 5 x PCI Express 2.0 x16
(2 x16, 2 x8, 1 x4) and 1 PCI Express x1 slot.
http://www.newegg.com/Product/Product.aspx?Item=N82E16813130274 (http://www.newegg.com/Product/Product.aspx?Item=N82E16813130274) - $195

AMD Phenom II X4 840 3.2GHz
http://www.newegg.com/Product/Product.aspx?Item=N82E16819103921 (http://www.newegg.com/Product/Product.aspx?Item=N82E16819103921) - $105

G.SKILL NS 4GB (2 x 2GB) 240-Pin DDR3 SDRAM DDR3 1333
http://www.newegg.com/Product/Product.aspx?Item=N82E16820231394 (http://www.newegg.com/Product/Product.aspx?Item=N82E16820231394) - $40

Seagate Barracuda 7200.12 ST3320418AS 320GB 7200 RPM 16MB Cache SATA 3.0Gb/s
http://www.newegg.com/Product/Product.aspx?Item=N82E16822148469 (http://www.newegg.com/Product/Product.aspx?Item=N82E16822148469) -$35

Antec TruePower Quattro Series TPQ-1200 OC 1200W - 228A on 6x 12V Rails
http://www.newegg.com/Product/Product.aspx?Item=N82E16817371039 (http://www.newegg.com/Product/Product.aspx?Item=N82E16817371039) - $239.99

Total for Base System: $615

Multiple 120mm Fans of your choice -$20-$50+

So here's the base system. No case needed really. Throw in some 120mm fans as needed. You have a 5 PCIE slot case. Sure they don't all run at x16, but we're not gaming, we're BTC mining which as I understand requires very little bandwidth, much like Folding at Home. So I'll say that's a moot point. You'll need a PCIE extension ribbon for $5-$20+ to fit in all dual-slot cards. There's also a PCIEx1 slot, which I've read can be modified relatively easily to accommodate another GPU, so for this theoretical build I'm going to include that.
I chose the phenom x4 because running two clients on my dual 5870, with an i7 920 @ 3.8GHz used 12-13% of CPU per client.
Running windows 7 and my 2 clients uses almost 2GB of RAM, so I chose 4GB for this setup.
Cheapo hard drive, not an issue.
As for the PSU, I would think this PSU could handle 5-6 5850's. Estimating each 5850 at ~150W draw each comes out to 900W for 6 cards. Estimate the CPU at ~100W and we have some room for error. Also this one has 12 PCIE 6pin and 8pin connectors, saving us some trouble.

Let's finish this calculation with 6x 5850's.

6x Sapphire Radeon HD 5850 XTREME 1 GB
http://www.amazon.com/Sapphire-Radeon-PCI-Express-Graphics-100282XTREME/dp/B004W75ATI (http://www.amazon.com/Sapphire-Radeon-PCI-Express-Graphics-100282XTREME/dp/B004W75ATI) - $900

$900 + $615 = $1515

Now let's breakdown the Mhash/s. I personally have 5870's, not 5850s so I'm going off of my expectations from a similar card and from what I have read around the place. These 5850's seem to be the biggest bang/buck if you are buying NEW. I've seen people pushing 5850's to above 350 and people leaving them at lower. I'm going to assume if you're dropping this much money on such a complicated rig, that you are going to overclock them and be skillful enough to do so.

A 5850 could make ~350Mhash and are ~$150. 2.33-Mhash/$1
A 5870 could make ~400mhash but are ~$200. 2-Mhash/$1
A 5970 could make ~800Mhash but are hard to find and could be anywhere from $500-$800. Let's say you find one for $600. 1.33-Mhash/$1
A 6990 is ~$700 and can make up to ~800Mhash. 1.14-Mhash/$1
A 6870 looks to be maybe $175 and gets ~300Mhash. 1.71Mhash/$1

That's about it for the best cards out there. Of course 5850's are a little less efficient power-wise compared the to 6xxx series, and I'm not taking power into account. But I think overall the 5850's increase productivity will easily pay for it's slightly increased power consumption.

So we have a $1515 system with 6x5850's @ 350Mhash/s, or 2100Mhash/s.
So the system overall is 1.386Mhash/$1

Of course I have sacrificed density by going with single card systems. I think going with all 6990's is doable, but at a cost. 6x 6990's = $4200. Let's say you found a good deal and somehow got them for $3900. Well we basically doubled power consumption. Going off the specs of the 6990 being rated for up to 375W, let's say it draws 300W.  That's 1800W + the system itself so maybe 2000W to be safe. We'd need a second PSU for ~$150 for a 1000W.
So $615 for base system, + $3900 for cards +$150 for another PSU = $4665.
6x 800Mhash = 4800Mhash.
That's $1.0289Mhash/$1 for a 6x 6990 system.

I'm not going to write it up but a 6x 5970 system would get AROUND the same Mhash and cost AROUND the same.

For the $4665 price of the 6990 system I could buy 3 of the 5850 systems. Instead of $4665 for 4800Mhash I would pay $4545 for 6300Mhash.
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I'm just having some fun here theorizing stuff. I didn't hunt around too much for prices but went with averages. I'm taking into account moderate to heavy overclocking on all of the cards, and went with rough (though I believe they would prove accurate with more research) power calculations. I already stated I left out electricity costs and I'm not factoring into account profit at all, that's why I gave all values in Mhash or Mhash/$1. So far 1.386Mhash/$1 is the best I can come up with.

Feel free to comment and critique. Just having some fun here.

I have a machine with 6 gpus. Your cpu and ram are way over spec. Think Sempron 140 and 1 GB RAM. Also 3x 5970s is the way to go.

Oh I see you said the ram is for windows. Use linux :)

Also the GPU limit for Windows is 4 GPU's (or 2 dual gpu cards) and 8 GPU's in linux (or 4 dual gpu cards). 6 dual gpu cards is nice but not possible for either system.

Also not counting the cost of a windows license.

Ah that's right. Well let's say it's linux instead then. Forgot about the GPU limits.


Really? Maybe's it's just in windows that each client uses up about 10% of the CPU. Well that would shave off $50+!

3x 5970's still comes out to be less efficient than a system with 6x 5850's. Just the 5970 in itself has a lower mhash/$1 ratio than the 5850, and that's if you can even find a 5970 at a decent price.

That's a bug with the OpenCL core (the driver itself). Nevertheless, you still only need minimal cpu and ram for a miner. The cpu loading, even though it is very real, won't affect your hashing power.


$/Mhash isn't the only thing to consider. Power efficiency is much more important in the long run, and 5870/5970s are more power efficient than 5850s. Although yes, these are harder to get your hands on.

Check the post. You'd have to use a PCIE extender and then mod a PCIE1x slot. It's doable, but could be difficult.

A 5970 is rated at 300W while a 5850 is rated at 150W. So energy-wise, a 5970 would be 2.67mhash/W while a 5850 would be  2.33mhash/W.
So at if you wanted to pull 1000mhash/s with 5970's you'd have about 375W from the cards alone. With 5850's at 1000mhash/s you'd need 429W for the cards alone.
Using the mhash/$1 calculations the 5970's at 1000mhash/s would cost $751. For the 5850's it would cost $429.
The 5970 setup would save you almost 55W, but would initially cost $321 more for the hardware. Using 55W less, it would save 1.3KWh/day, or 481.8 KWh/year. Let's go with a rate of $0.15/KWh. You'd save $72.27 in electricity with your setup. It would take you 4.44 years to justify the energy savings. The hardware for your setup is about the same, maybe $50 less for a mobo with only 3 PCIE slots, but the PSU would be nearly the same.
Using fractional GPUs in this calculation, but the numbers are still valid.

Your numbers are off. 700 Mh/s on a 5970 with stock voltage is realistic, 350 on a 5850 isn't. Even less with 6 of them in the same box. Think 320 top and even. Overall, a 3*5970 would be at least 150-200 Mh/s faster than 6*5850.

My remark wasn't mainly about the 5970, but the 5870, with which the maths becomes way different. Consider how much cheaper it is to get 2 of those than a single 5970. They're not as power efficient than the 5970, but more than the 5850. To get 350 Mh/s out of a stock 5850, you need to run it at 900mhz core, that's a 175mhz overclock on stock voltage. To run a 5870 at 400 Mh/s, you need a 90Mhz overclock. You have to consider feasibility. I was considering monster overclocks for my first rig, but you shouldn't, it's not that simple.

You also have to consider 2 others things: the 5850 is a middle end card and has already a low resell value compared to the 5870 and 5970. Of all the price decaying that computer hardware undergoes, the high end parts are the ones that resist the test of time the best. When the better cards are coming out and they are outrageously better while consuming the same power, you will need to upgrade, so the resell value of your cards will matter in the total equation.

Lastly, this isn't much, but by running 3*5970s, you don't need a 6 slot mobo nor the PCI-E extensions.

700 Mhash/s on 5970 at stock freq and voltage are not realistic. Fyi the card has 725 or 735 MHz per core, and this barely stables the mhash/s at 280 with BFI_INT. At 755 the card stables between 300 and 315 Mhash/s. Anyway most of miners use SDK 2.1 which is not so problem-free under Linux.

I agree with the part about pc components prices.

Not stock frequency, only stock voltage. A 5970 has two 5870 GPUs ran at 5850 speed and voltage, i.e. 725 Mhz core and 1.09v, when a 5870 is 850 Mhz and 1.162v. I've ran my own 5870s at 900 Mhz at 1.09v, and some have reported 950+ Mhz at 0.95v. I don't know if those crazy numbers are true, but from my own experiment on a 5870 gpu, it will hold 850mhz core at 1.09 no problem, which is what you need to o/c the card to in order to achieve 700 Mh/s.

I currently own a machine that has 4 x 5970  and I think going with dual gpu card is really the way to go if you are planning on future expansion. Personally this one rig served me well and I'm planning to sell it shortly before the next huge jump. But if I had to build rigs now, I would for sure go with a dual gpu cards from the start if possible. 

Well 5870's are rated at 188W while 5850's are 150W. I have two 5870's atm, I can get them up to about 990MHz with a voltage of 1.2v individually. That 90MHz overclock required a voltage increase. There's not much efficiency difference between the two. 2.13mhash/w for 5870 and 2.33mhash/w for 5850.

And I stated in the my post that I was using high end overclocks. The title does say "monster", all of the overclocks are achievable with some effort. My 5870's can reach up to 1GHz, but I start getting diminishing returns on gains in frequency per voltage increase and I haven't been able to tweak them enough. Maybe this crowd isn't as used to overclocking as me, but I like to get the most out of my hardware. Considering the 5xxx series is considered safe by many to run at up 1.3v, these overclocks are doable. Yes the overclocks would increase power consumptions, but I'd have to argue that increasing mhash by increasing power consumption is a cheaper alternative than increasing mhash by buying hardware.

Resale value of all of the 5xxx series is going to drop. 5870's can be found on forums used for as low as $150 and 5850's for as low as maybe $100. Either way you're going to lose about the same amount with these cards. Sure the 5970 will have a better resale value since it's an extreme card, but I don't think it will be significant. Also take into account the wear and tear on running these cards 24/7 will have on their resale value (if you're honest).

And I mentioned the part about the 3 slot PCI-E mobo, take $50 off the cost of that setup for a cheaper mobo. Still leaves a significant gap.

For stable mhash/s I just bought SO versions - 950Mhz, but they are the best 5800 gpus so definitely they need their stock 1.1163 V

Underclock mem. to 300 and 5970 can do 312 Mhash/s per core on stock clock freq. (BFI_INT latest poclbm or phoenix 1.4).

This rig and 2 more are under Windows so it's not practically wise to lower the memory so much because the fuckin "good" written driver crashes often.

Oh, on linux, SDK 2.1, it is rock solid 725/300 312 mhash/s ... sucks to windows eh?

Wasted a lot of time installing different tools for freq/voltage control ;D Sapphire Trixx, MSI Afterburner, Evga Precision, Gigabyte Easy Boost, etc... In each one you must carefully manage the voltage readings so in others there are no problems (Afterburner and Precision have option to desynchronize the settings between cards) But it's still madness :o

Have a rig with 2 5970s.

At 725/300 power is 615W (has 8 HDD and some monster fans).  Bumping to 830/300 is ~680 Watts.  All this at stock voltage.

725 gets me 312Mh/s and 830 gets 370Mh/s.  So for 65 watts I get ~ 232 Mh/s!

I would love to add another card with a pci-e extender but no clear place to mount it in this case (Norco 4020).  Don't think I can add another 5970 with a TX-950 PSU so thinking a 5850?

Appreciate anyone's thoughts...

I don't know where you are getting the Windows limit of 4GPU's. I've seen people running 8 GPUs (4 dual GPU cards) without any issues.

Why aren't people suggesting the 5830 in this? With a price of 130$ per card on Newegg ( http://www.newegg.com/Product/Product.aspx?Item=N82E16814102878&cm_re=5830-_-14-102-878-_-Product ) And according to the benchmarks it can top 290-300 mhash...why go with anything else?

You can get used 5850s for $120-130...

Wish I could find more 5970's!!!

Think in terms of scaling and supporting hardware price per hash. You want a standard box with no screwy extenders or anything like that. I can tell you from experience that if you put 3 or more 5970s on a single motherboard and overvolt them you're going to burn some pins off your ATX connector, but that's only something you'd probably do with water cooling. I'm not sure about motherboards with more slots, but in my experience the problem is with the ATX connector on the PSU side. I've burnt the plastic off 3 12v pins already.

Basically if you go desktop the most you can fit in a standard configuration is 4 dual-gpu cards, and in a rackmount server the limit is 3. Again, you may have PSU issues.

And yeah, the rest of the parts don't matter. In Linux if you use the right OpenCL stack you should have little to no CPU usage from the mining anyhow.