Topic: need help with hardware. (Read 1781 times)

Put it this way, I would not want to use anything less than that for 3x6990s, and definitely would not attempt to OC, but it should work.

It should all work fine.

That is a pricey mobo, but you should be able to handle three cards on it with no problem if you choose to expand.

The Athlon processor will work fine, but is overkill unless you also want to do some heavy-duty gaming... A Sempron will do.

The Thermaltake PSU you already have will do just fine, and if you are not that concerned with power costs anyway it might not really be worth it to you to get another PSU that is only slightly more effiecient. Use what you have I say, the Therlamtake has another advantage in that it has a higher power rating, which could come in handy if you want to experiment with overclocking, which can increase power consumption quite a bit.

The RAM is just fine, you could even go down to DDR3-1066 1 GB with no problem, again, that depends of what you decide to do with the rig besides mining...

The SSD is fine, but a USB stick will do.

There is nothing wrong with anything you have chosen for your rig, but if you want to save some dough there are some areas you can trim...

Same general advice. For the best cost/performance ratio look at AMD mobos and ATI GPU's. It is usually best to shop what is currently available on newegg.com as the specific items and their availability can change daily... I could give you part numbers but there would be no guarantee those same items would still be available when you go to order them.

 A Sempron processor with 1GB RAM should be more than sufficient. There is no need for on board VGA since you will be getting nice video cards anyways. You don't even really need a hard drive, I have built rigs that work just fine with a 16GB USB stick. An optical drive is nice for loading software and such, but you can keep power consumption down by leaving it out. You can find plenty of inexpensive mobos with a two or three properly spaced PCIe slots. Even PCIe 1x connectors can be used if you want to bother with custom mounting your GPU cards with PCIe 1x ribbon cables connecting them to the mobo. Those PCIe 1x cables can be had for about 5 bucks a piece on EBay and it might mean you can squeeze an extra GPU card in your case with an even cheaper mobo. You have to modify those ribbon connectors slightly by cutting a slot in one end so it can fit on the 16x card.

A lot of rig builders go caseless and that's fine if you really want to squeeze out the $/Ghash/s but I like cases protecting my precious hardware. A mid tower can do it if the configuration inside the case has enough room, I prefer a top-mount power supply because it usually gives you more flexibility in how to mount GPU cards, and I think it is better for airflow. Also for airflow I like more, bigger fans on the front of the case with filters to provide positive pressurization and to keep the airflow going all one direction.

Putting more than three cards in a rig can present a slight challenge as far as cooling goes. If you are using Windows you will be limited to four GPU cores, which means that if you get dual core cards like the Radeon 6990 or the 5970 you will never be able to load more than two cards in your rig.  I would rather go down the scale a bit and find GPU's that have a better cost/performance ratio like the 5850 or 5830, you can get three of those in a case pretty easily, just leave a space in between for airflow. in a Linux box you can use more than four GPU cores, but do not mix Nvidia and ATI cards, the drivers do not like to work together.

Your PSU will need to be big enough for all the GPU cards you want to run at their highest wattage consumption plus a couple hundred watts for the mobo and fans. Get the highest efficiency PSU of the proper size that you can find, and make sure it has enough PCIe power connectors, I like the 6+2 connectors for maximum flexibility, you will need two connectors per card. If there are not quite enough PCIe connectors on a power supply you like you can make it up if there are enough 4-pin mloex connectors, GPU cards usually come with adaper cables that connect two molex to one PCIe power connector, so if you have 4 extra molex connectors on your PSU you can power another GPU card if you run out.

Hunting for parts and figuring out your rig configuration is half the fun... So, have fun.

It depends on what you think will happen with Difficulty and $/BTC. I would still recommend using a part of your available funds to purchase some Bitcoins. I think it is useful to learn about mining and you can even make some money from it. But for one thing, if you run a mining-worthy rig all the time it will run up your electric bill, so take a look at the power requirements for your new rig and make sure this is something you can easily handle. Don't put it where you sleep unless you like the sound of fans running all night. It will also tend to heat up any room you put it in, so make sure you have a way to cool it and factor that into our power costs as well.

Basically, if you buy Bitcoins you are betting that the $/BTC will go up, which I think is a pretty good bet. And if you buy mining rigs you are betting that Difficulty will not go up too much, probably not a very good bet. But one thing that can happen is that the $/BTC will go down and keep Difficulty from rising too much, then your mining rig will give you more Bitcoins than it would have if Difficulty increased a lot. I am guessing that $/BTC and Difficulty will go up a lot. To hedge your bet it will be best to take part of your $1,600 and buy Bitcoins, and take another part of it to buy the most cost-effective rig you can manage.

Buy Bitcoin.