litecoin rig check (4x 7950)

[pajak666]

I am setting up second, stronger to previous one, mining rig targeting 3gh/s.
Can somebody take a look at components that I am going to use and check if everything is fine?

GPU's:
I have several choices, please point which card would you buy I am targeting this one:

• http://www.newegg.com/Product/Product.aspx?Item=N82E16814125414

Mobo&CPU:
Abit Kn9Ultra & AMD Athlon X2,2x2000MHz (I've choose such mobo bc I can get it second hand for a very nice price)
http://abit.ws/page/en/motherboard/motherboard_detail.php@pMODEL_NAME=KN9+Ultra&fMTYPE=Socket%20AM2

PSU:
I am not so sure if this one would be enough
this 1100W max 1320W?
http://www.coolermaster-usa.com/product.php?product_id=2753

or should I buy this one:
COOLERMASTER RS-C50 1500W max 3SLI
price difference is quite large fwiw so I really need to know which should I buy to run 4 x 7970.

RAM:
4GB ddr2

[computerparts]

Depending on what your previous rig is, this rig may be unsafe if you're plugging into a standard residential circuit.

[grue]

7970 = rip off. get yourself 7950s and overclock, much better MH/$.

You don't definitely don't need 1500W because 750W is AMD's recommendation for crossfire systems. The difference between 1 card and 2 cards is 250W, so the max each board can draw is 250W. Plus you're mining, so you're not using as much power as rendering/gaming.

Depending on what your previous rig is, this rig may be unsafe if you're plugging into a standard residential circuit.

1200W = 10A. some house's circuits are 10A per breaker, but most are 15A/20A

[pajak666]

but kettle for example uses stj like 2000w, wasching machine also sth about 2000w, and my circuit and breaker is fine.
or am I wrong about electricity, if you got sth good to read link it pls.

[grue]

but kettle for example uses stj like 2000w, wasching machine also sth about 2000w, and my circuit and breaker is fine.
or am I wrong about electricity, if you got sth good to read link it pls.

to be fair, those both use specialized plugs and are on seperate circuits.

[joshki]

1100w power supply should be okay from what I can find.

I guess you're planning on using risers and some custom case?  7970's are going to get you between 600 and 650kh/s, not 750.  You might get 700 if you can really push them, but it's not likely.  The highest I've ever been able to get is about 690, and they really weren't stable there.  Gigabyte 7970C's.

You're going to need more than 4GB ram for four cards.  At least double it.

There are better motherboards if you're going to run four cards off of one.

[kendog77]

I concur that 7970s are a poor value for mining. 7950s offer almost the same performance at ~$100 less per card.

My Gigabyte 7950s run at ~605k at stock speeds (1000/1250). My Gigabyte 7970s run at ~630k at stock speeds (1000/1375).

In my experience, the 7970s also run so hot that they don't overclock nearly as well as 7950s.

[kendog77]

"You're going to need more than 4GB ram for four cards.  At least double it."

The statement above is false. 4GB of ram is plenty for four cards if you're using cgminer. I believe reaper requires more ram, which is why people keep saying this, but I'm not sure why anyone would use reaper over cgminer at this time.

[btcminer021]

I get 645Mh/s with a Sapphire 7970 with stable OC

[joshki]

"You're going to need more than 4GB ram for four cards.  At least double it."

The statement above is false. 4GB of ram is plenty for four cards if you're using cgminer. I believe reaper requires more ram, which is why people keep saying this, but I'm not sure why anyone would use reaper over cgminer at this time.

He's planning to use it for litecoin, not bitcoin.

The rule of thumb for 7970s, as far as I can find, is 1.5GB per card.

[kendog77]

I know that he is using it for litecoin, and the need for more than 4GB of RAM for 4 cards is still false.

I have a litecoin mining rig running right now with 4GB of ram and 4 7950s using cgminer.

[joshki]

I know that he is using it for litecoin, and the need for more than 4GB of RAM for 4 cards is still false.

I have a litecoin mining rig running right now with 4GB of ram and 4 7950s using cgminer.

I'm a little new at this, but everything I can find on this forum says you need more ram to support higher thread concurrency to maximize the cards' potential. No reason it wouldn't run with less ram, but your thread concurrency would be limited.

When ram is probably the cheapest component, why scrimp to save a couple of dollars and limit yourself?

[grue]

I know that he is using it for litecoin, and the need for more than 4GB of RAM for 4 cards is still false.

I have a litecoin mining rig running right now with 4GB of ram and 4 7950s using cgminer.

I'm a little new at this, but everything I can find on this forum says you need more ram to support higher thread concurrency to maximize the cards' potential. No reason it wouldn't run with less ram, but your thread concurrency would be limited.

When ram is probably the cheapest component, why scrimp to save a couple of dollars and limit yourself?

it's still a waste of money. besides, if he doesn't have enough ram, he can always buy more.

[mxmz.in]

Need for more RAM is a false statement if you run cgminer. No powerful CPU is needed as well.

[kendog77]

My 4x 7950 rig is currently humming along at over 2400k, so it certainly doesn't seem to be limited by 4 gigs of ram.

When you're building one rig, I guess it doesn't matter that much. I have a couple, so I don't like wasting money on things that aren't necessary for mining.

4x 7950s                 = $1200
CPU / mobo             = $150
USB Drive                = $25
4 gigs ram               = $25
1200W Power Supply = $150
Linux Ubuntu 12.04    = free
Crate case / risers     = $50
Total                        = $1600 for 2400k

You can also sell the Never Settled bundles and bring down the cost even more.

This guide by tacotime is a good place to start:
https://bitcointalk.org/index.php?topic=163306.0

[joshki]

My 4x 7950 rig is currently humming along at over 2400k, so it certainly doesn't seem to be limited by 4 gigs of ram.

When you're building one rig, I guess it doesn't matter that much. I have a couple, so I don't like wasting money on things that aren't necessary for mining.

4x 7950s                 = $1200
CPU / mobo             = $150
USB Drive                = $25
4 gigs ram               = $25
1200W Power Supply = $150
Linux Ubuntu 12.04    = free
Crate case / risers     = $50
Total                        = $1600 for 2400k

You can also sell the Never Settled bundles and bring down the cost even more.

This guide by tacotime is a good place to start:
https://bitcointalk.org/index.php?topic=163306.0

That's a great guide, and he says to use 8GB of ram...

[kendog77]

If you want to waste your money on RAM for a litecoin mining rig that isn't need, go ahead.

I'm done. 

[pajak666]

ram isn't an issue since it's quite cheap and I got plenty of ram which I can borrow from my current pc to see how much do I really need and post solution.
anyway I've decided to go with those cards:
GV-R795WF3-3GD
http://www.newegg.com/Product/Product.aspx?Item=N82E16814125414

anyone got some experiences with them?
expected hashrate?
you think they are good choice?

[kendog77]

I like the Gigabyte 7950s, and actually have 7 of them, but they do run hot inside a case if you don't have very good airflow.

Whichever card is plugged into PCI-E slot 1 also seems to run very hot, so they do much better in an open case using risers.

They come factory overclocked at 1000/1250, and do over 600k mining litecoin without additional over clocking.

I really like these cards, but keep an eye on temps if you use them in a closed case and plug the cards directly into the mobo.

[miningdude]

The RAM requirement/misunderstanding for Litecoin mining is directly related to the mining software being used. If you use Reaper, you need extra RAM, however cgminer will run 4 cards just fine on 4GB of RAM.