Proposed mining setup

[zackclark70]

7970s might get a higher hash rate but they use more power ( 7970 700kh 250w+)  (7950 630kh around 210w)

7950's use around 260W overclocked while the 7970 uses about 310W OC'd.

120 more watts is only around $13 more a month if your rate is $0.16/kWh and you get around 150kh/s more.

It's all personal preference I guess

my 7950s run at 1050 core 1250 ram 1.050v 630-640kh with a 3 card rig under 720w from the wall and a 4 card rig under 920w from the wall

[FiiNALiZE]

7970s might get a higher hash rate but they use more power ( 7970 700kh 250w+)  (7950 630kh around 210w)

7950's use around 260W overclocked while the 7970 uses about 310W OC'd.

120 more watts is only around $13 more a month if your rate is $0.16/kWh and you get around 150kh/s more.

It's all personal preference I guess

my 7950s run at 1050 core 1250 ram 1.050v 630-640kh with a 3 card rig under 720w from the wall and a 4 card rig under 920w from the wall

Every card is different.

I have to OC my 7950 to 1350ram to get it to 580kh/s with 6% powertune.

lol I got a bad card I guess.

[zackclark70]

7970s might get a higher hash rate but they use more power ( 7970 700kh 250w+)  (7950 630kh around 210w)

7950's use around 260W overclocked while the 7970 uses about 310W OC'd.

120 more watts is only around $13 more a month if your rate is $0.16/kWh and you get around 150kh/s more.

It's all personal preference I guess

my 7950s run at 1050 core 1250 ram 1.050v 630-640kh with a 3 card rig under 720w from the wall and a 4 card rig under 920w from the wall

Every card is different.

I have to OC my 7950 to 1350ram to get it to 580kh/s with 6% powertune.

lol I got a bad card I guess.

I get the same on all 83 cards give or take 1-2%

[fishy]

Don't bother with the APU, the GPU in them won't mine for shit.

Well, if you are short on money and can only start with one GPU card, then the 115 MHash/s SHA256 / 70 kHash/s scrypt of the APU  is a nice extra. But if you have the money to get 4 7950 that will give 2400 Mhash/s SHA256, then it isn't much extra. Then I would look for a low power CPU instead, because the GPUs pull a lot of power already. APUs are nice when you want to build up a mining rig over a longer time.
For Scrypt you should have the same amount of RAM as your GPU cards, so 4x 3GB = 12 GB. I would say 16 GB should be good as the operation system and the mining software also need a little memory.

I'm building it in sections, over time, so I guess I'll keep the APU for the extra hash power in the beginning.

[fishy]

This should be your setup:

Motherboard: http://www.newegg.com/Product/Product.aspx?Item=N82E16813157262 $100

PSU: http://www.newegg.com/Product/Product.aspx?Item=N82E16817256054 $289 (After rebate)

GPU: http://www.newegg.com/Product/Product.aspx?Item=N82E16814202008 $309 (After rebate) (Same as 7950!)

CPU: http://www.amazon.com/gp/product/B0040BPHJO/ref=oh_details_o07_s00_i00?ie=UTF8&psc=1 $30

RAM: http://www.newegg.com/Product/Product.aspx?Item=N82E16820139077 $46


I know you wanted 7950's but right now the 7970's on Newegg are the same price, and they give you more hashpower/$.

However, you'll need a better PSU if you want to overclock (and the 7970s uses more power anyways), which is why I chose the 1500W.

It's pricey but you can use two smaller and cheaper PSU's if you know how to connect them.

Oh and also use powered risers just in case.

This took me a while to compile so I'd appreciate a donation

This is my first time building a rig, what are powered risers for?
Also I hear you need "heatsinks," what are they for?

Finalize, you have a devcoin address?

[Trillium]

This is my first time building a rig, what are powered risers for?
Also I hear you need "heatsinks," what are they for?

Finalize, you have a devcoin address?

There is a usually unknown but still inherent limit to how much current a motherboard can - in total - pass to its PCI-e connectors.

A full-power-rated PCI-e full length slot by international standard can supply at least 75 watts to the card. This is not enough though of course for most good cards, so we have 6 and 8 pin molex to help supply more power.

The problem becomes, that if you are running a lot of cards then you don't know how much your motherboard can safely supply via PCI-e to all the cards. Maybe its just 75 watts? Maybe its 400? In any case it is a unknown and it is a risk.

The solution is to bypass some or all of the power connections via the PCI-e connector and instead use risers that have power connectors spliced on, so you can power it 'directly' from the PSU just like with the 6 and 8 pin molex connectors for the card.

This decreases risk of: random power transistors and capacitors and other parts on the motherboard failing due to overheating or worse, just exploding, and it arguably increases stability in the case that your motherboard can physically take the load but still supply insufficient current.

There are threads here about users who have charred components on their motherboards or melted/charred the main motherboard ATX connectors or cables.

https://bitcointalk.org/index.php?topic=161242.0

https://bitcointalk.org/index.php?topic=102890.0