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Author Topic: 3x 6990 Rigs  (Read 1212 times)
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June 23, 2011, 01:46:57 AM

Hello all , I am certainly a noob. I have been reading a lot of this forum for the past several weeks so I think I have learned a thing or two. I currently just am mining with a few simple computers churning out a whopping 100 Mhash/sec. I have no confusion about hitting a jackpot here and building a mining rig to retire on, but I do appreciate the entire concept of bitcoin and I want to participate while at the same time find an excuse to buy a bunch of video cards and build computers and participate in this community - we all need hobbies!

I figure if I am going to get in, get in right! I intend to get 3 6990 when they come in stock (i know, super hard to find) and build a decent rig out of those hoping to get to 2 Ghash as an output. I do not pay electric costs. Anyone recommend a good motherboard/PSU/case for this purpose?


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Lea Calot
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June 23, 2011, 02:41:47 AM

Hi Arashd,
hey, same here. I just ordered my list of goodies. I went for 2x6950s (and still reserve the option to buy more later) instead of 6990s because the cost-reward factor was still to high. You can get 6950s in my area for 250$, but the 6990s are way up in the 700$-range.

What you need is a board that can host those graphics cards side-by-side. They usually take two slots, so the PCIe slots should be spaced further apart.

This board did it for me:
You can stick in 4 PCIe x16 graphics cards side-by-side. See the nice little picture in the promo.

Since most of the Bitcoin operations do use the GPU, I bought an AMD Phenom II x2 250, which was on sale. I also stuck in a 4GB DDR3 module.

What you need next is at least a 750W power supply that can power your 3 cards (or in my case later on 4). This one can do and was on sale at my retailer:

For the case I recycled an old server case that formerly hosted an old Dual-Xeon server.

I hope it helps. If I were you I wouldn't throw my life savings into the 6690s, at the current bitcoin mining difficulty it'll take quite some time until you get your return on it, even with 2Ghash/sec.

Here are some numbers with $/Mhash figures and more ideas about rigs:

Feel free to donate some coins to support P2P fault tolerance research: 12RZ1yWi4KT5JU81EePo52HS3mrhSCXswm
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June 23, 2011, 03:11:55 AM

You can also buy PCIe 16x and/or 1x extenders.

I was able to pick up a few here:

I'm able to run my cards on a board with 2 PCIe x16 v1.0 slots and
1 PCIe 1x slot.

If you use the extenders you'll have to find an alternative way to
mount/support the cards since they won't be slotted directly into your
motherboard. I built a frame using PVC pipe and hang the cards
from it using zip ties.

Good luck,

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June 23, 2011, 07:58:30 AM

Note that the 6990 consume about from 375W stock to 415W overclocked.So You'll need a Power supply unit of at least 1200W(if not more!!)to power 3 cards...
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June 23, 2011, 09:04:15 AM

for 3 6990 you need at least 1200W thats true!
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June 23, 2011, 09:43:58 AM

plus a way to keep them cool...

3 x 6990 overlocked will be belting out a lof of heat.

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June 24, 2011, 03:18:22 AM

Yeah, I'm finding it tough to keep 2x6950 cool even with a ton of case fans; I have no idea how 2 or 3x6990 would work without water cooling.
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June 24, 2011, 03:21:48 AM

i water cool my 5970 and 5870 they stay nice and cool but let me tell you it dumps a ton of heat into my room.

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