I did it

[cvicisso]

Ok - took the plunge.  Here's what I ordered from Tiger Direct for ~$1400:

3 x 6950 2GB
1GB DDR3
890FXA-GD70 mobo
Sparkle 1250w Modular Power Supply 80+ Gold
AMD Sempron 145 2.8Ghz
***Cooler Master HAF X ATX Full Tower Black

The case was probably overkill, but DAMN! it has a lot of fans on it!!  I couldn't resist - and heard great reviews.  Plus, I had to cram everything into something, right?

Anyway, I'm hoping for 1GH/s (at LEAST).  I have a crap load of HDs laying around, but I have even more thumb drives.  What's the preference?

Also - what software should I use (I'm leaning 99% UNIX).  One I start mining these suckers, I can 'reward' folks who help me out.  I'm really new at this, and it would be worth it to me.   

OBTW - with those extender cables (or whatever) I was reading about, how many GPUs can I fit in this case/mobo combo.  I have PSU and cooling to spare, but not sure about the space available.  After the initial rig is paid for, I'll be adding GPU(s).

[dingus]

You'll need those fans, trust me. About your hard disks / thumb drives... back up your wallet.dat on each hard disk / thumb drive so you have little chance of losing your coins ( at least from hardware failure ). With that mobo you should be able to space out those 3 cards enough to counter act the heat they produce. I have that same mobo with 5970s instead so I know how hot they can get sitting right next to each other.

[bcpokey]

You'll need those fans, trust me. About your hard disks / thumb drives... back up your wallet.dat on each hard disk / thumb drive so you have little chance of losing your coins ( at least from hardware failure ). With that mobo you should be able to space out those 3 cards enough to counter act the heat they produce. I have that same mobo with 5970s instead so I know how hot they can get sitting right next to each other.

The HAF X isn't that great for gpu cooling, but it's not bad. The 9 slots give you plenty of room to space out the cards and still not bump into your PSU which will be nice. If you backup your wallet.dat make sure to encrypt it. Would be a shame to have someone nab a rogue thumbdrive with all your coins.

[aznsniper911]

You'll need those fans, trust me. About your hard disks / thumb drives... back up your wallet.dat on each hard disk / thumb drive so you have little chance of losing your coins ( at least from hardware failure ). With that mobo you should be able to space out those 3 cards enough to counter act the heat they produce. I have that same mobo with 5970s instead so I know how hot they can get sitting right next to each other.

The HAF X isn't that great for gpu cooling, but it's not bad. The 9 slots give you plenty of room to space out the cards and still not bump into your PSU which will be nice. If you backup your wallet.dat make sure to encrypt it. Would be a shame to have someone nab a rogue thumbdrive with all your coins.

With stock cooling then it is an okay. I also have the HAF-X but I modified the cooling. I use the fan adapter inside and I took out the side fan adapter and use zip ties to attach two high speed 120mm fan.

[kcobra]

Make sure you read up on how to flash the 6950 cards to 6970 (basically unlocks the shaders). I believe you have the have a reference designed 2gb card.

[aznsniper911]

Make sure you read up on how to flash the 6950 cards to 6970 (basically unlocks the shaders). I believe you have the have a reference designed 2gb card.

Even with reference, some cards aren't even unlocking since they are supposedly laser cutting the cores.

[horrorshow]

I've always wondered why they do stuff like this. Why do they laser cut the cores and limit it?

[1.21gigawatts]

they want you to spend more money and buy the 6970

[snoopytime]

Why dont they make them all 6960s and sell them all with it working for in between the price of 50s & 70s lol

[dingus]

They (ATI/AMD) did this kind of thing to the x2 and x3 Phenom 2s. You used to be able to buy a dual core x2 and unlock it to a quad core; same thing with the tri-core x3, but they made it so you couldn't do that after awhile because I suppose so many people caught on to it.

[compro01]

I've always wondered why they do stuff like this. Why do they laser cut the cores and limit it?

one of two reasons

1. the cut off cores don't work properly, which is why they are a 6950 rather than a 6970, and thus shouldn't be used.

2. the cores work fine, but are deactivated for demand reasons, and they want them to be the same as the above cards for the sake of fairness and also to avoid dumb people complaining when they flash their cards to unlock them and find they got one of the type-1 cards.

[Yanz]

Anyways what the OP was asking:

1) You should be able to get at least 1GH/s. Probably 1.2 because I have a 6950 (unlocked and OC'ed to 940 core) doing 410.
2) I tried Ubuntu for mining but the overclocking capabilities weren't as good. MSI afterburner is pretty awesome. If you don't plan on OC or can figure out how to do it on linux then that is probably the way to go.
3) You probably won't need those extender cables unless you plan on having the cards hanging out of your case. You can fit 4 on that mobo without extenders but if you extend the top slot you can uncover that pcie 1x slot giving you 5 cards on that mobo.

[cvicisso]

Thanks everyone!  I can't wait for this thing to arrive and fire it up! 

I paid [alot] extra for the HAF X for the cooling, but if it still becomes an issue, it has some options for increasing cooling rate.  I can add another top fan OR a cooler/radiator if necessary... We'll see what happens there, and I'll keep you posted.  Major potential issue is that I anticipate this will be LOUD and therefore will attempt running it in the [non-air-conditioned] garage.  It is summer time in VA Beach, VA - so I might be pushing the envelope for heat.  We'll see...

1.2 GH/s would be awesome!  When/if I break even, I'll add another card (or two) to the case/mobo (and maybe increase cooling somehow).  PSU (1250W) should be ok (right?).

One final question: has anyone had success mixing different GPUs?  For example, if I somehow find a 5970 to throw in that extra slot, would it work with the 3x6950s?

Thanks again!  You'll be hearing a lot from me in the near future - mostly questions, but hopefully I'll be able to contribute more as well as my knowledge level increases.  At a minimum, I'll share mistakes and best-practices.  And I DO intend to reward folks who are willing to hold my hand along the way (that's how I roll - it's the cost of doing business).

[Yanz]

I think your PSU is fine for now. I'm not sure about 5 6950's...they pull about 200watts each + mobo and other crap.
Funny you say 5970, I had a 6950 for gaming and then I picked up a cheap 5970 off CG. Apparently cards of different series don't play nice. (ie you can only get other 69xx cards) I kept getting BSODs and driver issues in the end I just put in a spare rig and called it a day. If anyone has a solution I'm all ears.

Donations would be awesome  . I'll try to help you (and anyone else) as much as I can.

[kokojie]

PSU 1250W is probably overkill. You'll do fine with 1000W,
1250W can accomodate 4 x 6950

[cvicisso]

PSU 1250W is probably overkill. You'll do fine with 1000W,
1250W can accomodate 4 x 6950

Perfect.  I got a good deal on the 1250W (it was packaged with the HAF X case for same price as HAF X + 1000W).  I don't mind having too much.   

[cvicisso]

I think your PSU is fine for now. I'm not sure about 5 6950's...they pull about 200watts each + mobo and other crap.
Funny you say 5970, I had a 6950 for gaming and then I picked up a cheap 5970 off CG. Apparently cards of different series don't play nice. (ie you can only get other 69xx cards) I kept getting BSODs and driver issues in the end I just put in a spare rig and called it a day. If anyone has a solution I'm all ears.

Donations would be awesome  . I'll try to help you (and anyone else) as much as I can.

Great advice (about not mixing cards), and...

Deal!  Let's work together (as you're able to) and I'll be sure to throw some love your way when I'm up and running and the BitCoins start coming in.

[cvicisso]

Forgot to ask: This rig will probably [99.9% sure] be AWAY from my physical router (too loud).  Since I'm not plugging in any extra guts like a wireless card, should I get a wireless 'extender' for my wireless network?  Will this be enough [bandwidth] - or does this thing really need TRUE Gigabit hardwire capability?

[Yanz]

No, it's not bandwidth intensive at all. Just make sure it's reliable though. Wouldn't want it losing connection in the middle of the night would we now 

[phillipsjk]

Will this be enough [bandwidth] - or does this thing really need TRUE Gigabit hardwire capability?

If you have to ask that question, I am jealous of you Internet connection.

Yanz is probably correct: you likely want some kind of wired connection if possible, but the speed is not critical.