Mining rig question:

I am wondering how I should connect my Sapphire Radeon 7950 cards to the PSU. There are 2x6 pin connections on the top of each card.

If I use only one 6 pin connection at the PSU end that splits into 2x6 pin connectors at the card end, am I correct in thinking that this will only
provide each card with 75 Watts, rather than the 150 that it wants to get through the 2x6 pin connectors. That would put a tremendous load
on the motherboard (through the 24 pin connector).

So, do I need to use separate 6 pin connectors/cables for each of the 6 pins of the card?

Sorry for being so ignorant!

One of my mining rigs was mining successfully for about 6 weeks. Yesterday, I found it silent and not running. So I switched off the psu and then turned it back on.

Immmediately, there was a large orange spark in the the area where the psu connects to the motherboard, so I shut it off and took apart the rig to inspect the connector and pins, to see if anything was obviously burned out. To my untrained eye, the pins and connector look okay, but obviously I am only seeing what is visible from the outside.

Another strange thing that I noticed in the weeks leading up to the spark- my psu would occasionally make subtle clicking sounds (one click every couple of seconds), almost like the sound of water dripping.

Is this an obvious short on the Mobo or can it have something to do with the psu? I am hesitant to try out another psu with the same mobo.

My hardware: 4 x sapphire 7950's- two on the mobo, and two with unpowered risers (I suppose this could have overloaded the mobo). psu is a Corsair AX1200i, and the mobo is an MSI 990-FXA GD65.

Thanks in advance for any suggestions.

I am new to primecoins (and more generally crypto currencies) and have a few questions:


A) I am trying to understand how to get the block header hash from a given primecoin block.

For example, using primecoind, I can get block info:

./primecoind getblock b56ce048d64313380d2a947cbb99bda97825646d89c6fd4222d154fc7f145bdd
{
    "hash" : "b56ce048d64313380d2a947cbb99bda97825646d89c6fd4222d154fc7f145bdd",
    "confirmations" : 347122,
    "size" : 198,
    "height" : 10000,
    "version" : 2,
    "merkleroot" : "478aa31ca6011384884c60a5a3c864475640dfa546be26631f1cc58366b3d2ad",
    "tx" : [
        "478aa31ca6011384884c60a5a3c864475640dfa546be26631f1cc58366b3d2ad"
    ],
    "time" : 1373505507,
    "nonce" : 627,
    "bits" : "07a62bc2",
    "difficulty" : 7.64910519,
    "transition" : 7.97894430,
    "primechain" : "TWN07.ecf7e1",
    "primeorigin" : "3137429839290119515389894171750697301735643977360059424820833454775626872284966 6432245972690",
    "previousblockhash" : "835228e99c1617650f8d72a3167fc92a8a3cf4bebcf60860a645d5b5309f8f87",
    "nextblockhash" : "54d6ec1f98ba10f897f7d8ea0991a042438f38b066702fc53fa05b52f93c3525"
}

My understanding (?) is that the primeorigin should be divisible by the `block header hash' of the previous block.
But how do I determine the block header hash? I don't think it is the " "previousblockhash" which, in this example, is "835228e99c1617650f8d72a3167fc92a8a3cf4bebcf60860a645d5b5309f8f87" because when I convert this hex string to decimal I don't get a number that divides the given primeorigin.

B) I am also after a more detailed description of the primecoin specs. Sunny King's paper is very broad and not at the level that describes the particulars of implementation. For example, for the Cunningham prime chains, would the primecoin network accept any prime chains where the origin is *any* multiple of the block header hash (so long as the other requirements such as difficulty, size of primes etc are satisfied)? I noticed that primorials are built into the multiple in primecoind's search for prime chains, but I am guessing that it is not an actual requirement.

C) Also, I am trying to reverse engineer how primecoind searches for Cunningham chains. Can anyone point me to documentation or a description of the actual implementation.

D) Finally, what precisely do primespersec and chainsperday refer to here:
./primecoind getmininginfo
{
    "blocks" : 357131,
    "chainspermin" : 5,
    "chainsperday" : 0.02283714,
    "currentblocksize" : 4614,
    "currentblocktx" : 5,
    "difficulty" : 10.38302714,
    "errors" : "",
    "generate" : true,
    "genproclimit" : -1,
    "primespersec" : 854,
    "pooledtx" : 5,
    "sieveextensions" : 9,
    "sievepercentage" : 10,
    "sievesize" : 1000000,
    "testnet" : false
}

Thanks in advance for your help.