Bitcoin Forum

Hello, from my understanding, the bitcoin miners will allocate 1 core for each GPU

now given that each Radeon 6990 is two GPU's each, what should I expect (assume NO crossfire)

would A) with 3 Radeon 6990's attached to the system, only 3 cores of my quad-core CPU will be used
or
would B) with 3 Radeon 6990's attached to the system, it would be preferable to have 6 cores as all of my cores would be used

What if I had two CPU's on this motherboard :)

I can use a 1600W power supply, but I fear this may be oversaturated too (but I'm open to underclocking the CPUs)

You get heavy CPU usage under Windows when the cards are crossfired. But not under Linux. What is your exact motherboard?

And there is no way you can use 1600W with that system.

Well crossfire can only address 3 GPUs so that is one and a half 6990s..........

so I won't be using crossfire.

What power supply do you suggest?

For the most part if you have a dedicated mining machine under Linux you don't need to worry about the number of cores.  The CPU is engaged only for brief periods.   I have a 6990 running on my 12 Core box and each instance is using < 1% CPU.   Under poclbm use the "-f 0" flag.

I have my 6990 clocked @ 980/1260 and the whole rig (including two hex-core Xeons, a GTX480 running at full load and ten SATA drives) uses 850W - as measured from a watt-meter which is constantly attached.  Given that my 6990 runs around 350W a 1600W PSU will probably be fine.   You probably won't be hitting peak efficiency as most PSU's are designed to get the maximal efficiency (80%, 85%, 92%, etc) at the middle of their available load.  Also I tend to find that 120V PSU's > 1200 tend not to be designed for the higher efficiency specs.  220V PSU's however are more efficient - ie it's much easier to find 90% efficient 220V PSU's (and single voltage PSU's even more so but I'm getting off topic).

Jono

  

Jono,

Your thoughts? http://www.tigerdirect.com/applications/SearchTools/item-details.asp?EdpNo=2937371&CatId=5115

You can expect your investment to be wasted when difficulty increases again sometime next week. Seriously though what are you asking? Cpu cores have nothing to do with gpu mining.

computerparts, another thread shows that some clients use way too much CPU



where can I learn about difficulty?

First always look at newegg first  ;), best prices and normally better products.

Second Ultra is a cheap Tiger Direct brand, may sound good but its not the deal you think it is if it blows your 3 shiny 6990's.

I recommend Corsair, amazing company (tier one): THIS BABY (http://www.newegg.com/Product/Product.aspx?Item=N82E16817139014)

1: that was guiminer and he fixed it with the next update so you should be fine now

2: Right HERE (https://en.bitcoin.it/wiki/Difficulty)

1200W on load with 3xRadeons? you sure about that ?

also can Core i7 1366's work in any mobo that accepts 1366?  I know Xeons and Core i7's are the same silicon but there might be some other variable I didnt consider

Oh I see, so today it takes about 550Mhash/sec to generate a bitcoin, next week it could take 800Mhash/sec for one bitcoin

hmm

Save your money and buy bitcoins instead, It will take a long time to redeem your money you spent on the 3 x 6990's(I know because I bought the same thing). Anyway if you still want to mine then linux will be the only option for you just now, as the SDK kit for windows will only allow 4 GPU's to run.. Linux will allow all 6 GPU's to run and should yeild about 2000 MH/s upto 2400 MH/s with overclocking(not advised). the longer it takes to break even with the hardware the more you have a great chance of loosing your investment money. P.s I advise against any major overclocking as it could damage your hardware let alone void your warranty, which means a huge lose instead of a small lose. you will make more money and make it alot faster if your bought the coins instead of trying to make them at a profit.

Ok, here's my recommendation.   Austin is right, Ultra is a cheap brand...but it *will* work.   The Corsair 1200AX is a beautiful piece of equipment.  In fact I'm using that selfsame PSU on my rig right now but you are correct you might overload it.  If you assume 333W per 6990 that leaves you with only 200W for the rest of your rig.   If you *can* stay in that budget the Corsair is the better choice.  Otherwise go with something with a higher rating.  You *can* run PSU's over spec (I've personally run 350W's @ 500W for months at a time) but I'd be reluctant to do that with the 1200AX as well-built as it is. It's a single rail unit.  Which means there's some hunk of metal in there willing to source 10A through some conductor...like you. ;-)   So while I expect it to fail less, it has the potential to fail more spectacularly.  So I wouldn't push it.

As for the i7's check with the motherboard manufacturer. If it doesn't specifically list the CPU (Xeon or i7) you want think twice about using it.   The BIOS may balk when it tries to do something like upload microcode.  Which means although the whole system might be capable of running fine.  The BIOS won't complete the POST and it won't boot.  This has been known to happen with ES (engineering sample) CPUs from time to time.  The other gotcha is there are actually two forms of the 1366 physical socket.  Some Xeon based boards are built around the 1366-B socket configuration (this has a backplate on the bottom of the mobo under the CPU sockets) and a slightly different position for the retention screws.  It's different enough that many 1366 fan/heatsinks won't fit.  Make sure you know which one your mobo has and that your fan/heatsink explicitly states it supports it.

Edit:Some places with good info about PSU's:
http://www.jonnyguru.com/ (http://www.jonnyguru.com/)
http://www.plugloadsolutions.com/80PlusPowerSupplies.aspx (http://www.plugloadsolutions.com/80PlusPowerSupplies.aspx) <- Check out how clean the 1200AX's power curve is.

1600W power supply would be only enough for 2x6990s. It would be a waste to use three of them and underclock so much. It be much better to get extra power supply and use it for the third 6990. That way you can get the full potential from all the GPUs.

600-700W per 6990?  That's completely incorrect.  Even when OC'd there is absolutely no way a 6990 is sucking back that much.   As I've stated I have an actual watt-meter attached to my system all day every day and even when clocked @ 940/1250 the 6990 isn't using more than 400W at 100% load.   I double-checked this by shutting down each core and bringing them back up again.  (Revising my advice here: if you are OCing the cards then AX1200 is probably too little).

That said, there is something in what Dairoux is saying.  Often large PSU's are sold at a premium.  There's nothing wrong with using multiple small PSU's except for the space, mess and inconvenience of powering on something that isn't attached to your mobo.  Estonia has this mobile rack machine they use for folding which they built on the cheap.  Each 4U rack unit had 4x GTX 295 and instead of using a single large PSU they used multiple 850W units.  You could do the same.  Look for something Gold or Platinum rated.  Also if you have a 220V line or can have one installed.   The PSU will be even more efficient.

wait, you need a dedicated CPU core per GPU if you're running windows?!?!  wow.

Also, do you know if multithreading CPUs would count as 2 for this purpose?

I don't fold on windows but I expect that a logical core on a hyperthreaded system would be sufficient.  My understanding is that the CPU usage is just an idle loop.   Consuming CPU but doing very little.   As I've mentioned on Linux the actual CPU usage is insignificant.