Bitcoin Forum

I've been searching forums and IRC logs, along with plugging numbers into a spread sheet to figure out the best current GPUs to buy for a dedicated mining rig.

But there are a few questions I just can answer without experience.

I'm basing my performance numbers on the data here: https://en.bitcoin.it/wiki/Mining_hardware_comparison

Based on that, I think I could build a system with 4x 5870s for ~$1600 total and get around 1.4Ghash. Those cards are going for like $215 each now.

That seems more cost effective than 2x 5970s since I'm having a hard time finding those for less than $650 each. If I had to pay $650 for those cards, I think the best I can do is around $1800 total for that system. I realize some cost savings by getting cheaper MB, case and power supply, but the GPUs cost 3x as much for 2x the performance!. And then I'm doing like 1.2Ghash?

I don't see how the pricing adds up unless I can get lucky and score some used 5970s on ebay for a better price. (I did just see one go for $470 + shipping.)

Unless the thing I'm missing is cooling. I haven't tried to build a 4 GPU system before. Is it going to be impossible to cool a 4x 5870 system that's running 24/7?

Also sound may end up being a consideration depending on where I end up keeping this.

Any advice would be appreciated.

You would have to use flexible PCIe-extenders to connect four GPUs because if you plug them all directly into MB, they'll block ait intakes of each other.

And you can't plug them all directly because standart ATX system would accept only 7 cards (and each 5870 takes double space).

CPU + mobo + RAM = 175$, PSU = 150$, case or stand or wtv = 50$, misc items = 25$, 4x 5870s = 800$

You can probably squeeze it in a 1200$ budget

6990 at 700$ isn't too bad either

Can you recommend a case that would work with 4 5870's?

You're probably going to have to modify almost any case slightly to fit 4 cards into it.

I'd just use a test bench

For 4 cards you would need 3 spaces in between, so a total of 7 slots would suffice. Of course, for cooling you need extenders. 1x extenders are probably better for airflow and extra flexibility, and the 1x speed is not a concern for mining.

There are motherboards that can support 4 cards. For example, Gigabyte has motherboard GA-890FXA-UD7 with extended form factor that supports four double spaced cards: http://www.tomshardware.com/reviews/amd-890fx-crosshair-iv-formula-890fxa-ud7,2640-6.html.

However it is required to have the special case for such motherboard (XL-ATX).

Yeah, I was looking at the MSI 890FXA-GD70 and the CoolerMaster HAF-X. That combo should fit 4 cards. But Motherboard + Case is $365.

A cheap case + cheap motherboard could save $~250.

If I could get 2 5970s for under $600 each, then I'd come out ahead on the dual 5970 system with a cheaper motherboard and case.

Otherwise, assuming I could cool it, it still seems like the 4x 5870 system makes sense.

And yeah, I understand I could save more by building super cheap cases out of various other things, but I don't think I want to make that optimization.

What PSU are you talking about for 150usd that will power 4x5970 safely?

There are some Lian Li cases out there that have 8 card slots in the back.  I'll have to agree, though, that sandwich of 4 5970s would be crazy hot.  You'd have to take the case door off and stick a small box fan beside the computer and even then they would be a little hot.

Also, there are motherboards where the 7th slot is an x16 slot, which the Lian Li case would work with.  Front panel wiring be damned.

We were considering 4x 5870s vs 2x 5970s, not 4x 5970s.

nster suggested you could power 2x 5970s on a $150 PSU.

When I'm talking about 4x 5870s, I'm looking at the Cooler Master RSC00-80GAD3-US, which is about $240.

Sorry I missed that part, I was thinking 4x 5970 thats a huge difference. You should be able to power those for $150.
I like the ultra x3's and they have a lifetime warranty. The ST's are efficient as hell though... hmm

http://tpucdn.com/reviews/ASUS/EAH5970/images/power_maximum.gif

Corsair HX and AX series are very nice. Specially the AX1200, which can power 4x 5970, let alone 5870s (if downclocked and with a CPU that doesn't consume too much power, there is NO doubt about it), but would also be great if you are looking into the 250~280$ segment of PSUs

I admit 4x 5970s would be cutting it close on it, but keep in mind the numbers I have posted above are MAX Furmark power consumptions. Peak consumptions (max 3DMark 03) is here: http://tpucdn.com/reviews/ASUS/EAH5970/images/power_peak.gif

Difference between 4x 5870 and 2x 5970, power consumption. Almost 200w difference, even if the 5970's core will be OC to 5870 core speed the difference is still big. If your planning 4 cards on 1 motherboard, you should consider water cooling the cards.

That would be one hell of a WC setup - like dual 480s?!?

Yeah, after looking at the numbers more, I decided that getting 2x 5970s does make more sense. IF I can get them cheaply enough.

Maybe due to bitcoin mining, most 5970 I see now is 5-20 dollars more than the price a month ago.   ::)

at the price of WC the cards, you could build another miner...

Watercooling IS NOT cost-effective.

Why use a "case" when you can use a frame? http://darwinmachine.com/products.htm (http://darwinmachine.com/products.htm)

Just drill and tap some holes in a piece of aluminum to mount the motherboard. You don't even have to decorate it like in the example I linked to.

Isn't the 5970 the best mining card, due to the highest amount of shaders for lowest power drain?

That seems to be the consensus, but they are not that easy to find right now for a reasonable price.

http://www.bit-tech.net/hardware/motherboards/2010/04/27/msi-890fxa-gd70-motherboard-review/1

Could somebody explain to me what does "Expansion slots Four 16x PCI-E 2.0 slots (two 16x or four 8x)" means according to mining? Does it means that if I will use four HD 5870 then they will work on only half of their performance?

It has no impact on bitcoin mining...  Just on playing video games :)

x16 to x8 doesnt even have an impact in games :)

That's a good motherboard. Currently using it for my fan-cooled dual 6990 rig. I plan on adding more cards and will probably only end up hitting a wall due to my power supply and the amount of heat I can dissipate. You could run your cards in a PCI-E 1x slot and your Mh/s wouldn't be affected one way or the other. All the 1x/8x/16x denotes is amount of bandwidth available. Mining is computationally expensive, but very inexpensive in terms of bandwidth.

Thank you. Now it's clear.

With PCI-E extenders and DIY frame to hold everything together, no need for WC.   ;D

Look at some of the products on cablesaurus.  He's even got a *pci* to *pcie* adapter, which can then be used with the pcie extenders.  8 total GPUs even on a cheap motherboard is doable.  Also found this: http://www.amfeltec.com/products/flexible-pci-to-pcie-adapter.php

As far as case, $250?  Really?  Just get some aluminum L-angles from home depot for $16/8 feet, $5 for a bag of 100 bolts and nuts and a drill.  Assemble a cage from the L-angles to bolt the cards and optionally PSU to, put the motherboard on a non-static foam pad, use a $12 dual PSU adapter to get a ~1300 watts for less than a quality 1000 watt PSU.

get 12x 4U rigs, a 48U rack and cool your 16kW with an a/c. expected cost: around 30k eur without a/c. 3x 5990/6990 per rig, 1.5kW PSU (enermax has a 80+ gold 1.5kW PSU), random board/ram/cpu. you'll need 4x 32Amps for the rack and another one for your a/c. very space efficient.