Bitcoin Forum

So, having done a bit of research over the last coupla months, I'm gonna make me a sweet miner. I've ordered a mobo with 4 PCIe x16's, it'll have risers, a 5970 on the end of each (delivered by the 5970 fairy), and all juiced up with a 1250W 80+ Gold PSU. Shitty CPU, cheapest ram, basic NIC and a BAMT stick, phoenix and phatk2. Oh yes, I know my onions.

This post is not about that miner.

This post is about the cheap-ass £30 mobo I bought back in October when I'd just learned what a bitcoin was. I have had it running 2 5970's. I am going to give it a third. But I want to make sure I sew the pieces together properly.

It has two PCI slots, a PCIe x1 and a PCIe x16. The PCIe x16 has a riser and a 5970. That seems fine.

The PCIe x1 has a x1 to x16 riser with the other 5970 on it. That also seems fine. But could someone confirm for me that that's all OK? There's no power issues there, right? A x16 slot can supply 75W of power, but I dunno about a x1 slot.

Then there's the PCI slots. One of those has the network card. The other one is free... but not for long. My plan is to stick a PCI-PCIe16 adapter in there, like this one: http://www.virtuavia.eu/shop/pci-32-bits-1-x-pci-express-adapter-.html . Then have a x16 riser coming out of that, then stick the third 5970 (which I already have) on the end. Is there going to be a power issue here? The 5970 will get 225W fair and square from the 6-pin and 8-pin cables to the PSU. How much will it draw through the PCI slot? How much CAN it draw from the PCI slot? What will happen to the card if it can't get enough power? What will happen to the mobo if the card draws too much power? If one of these two misfortunes is to occur, how do I know which one it'll be?

Thanks for reading this far!

The card doesn't have to get the power through the slot, it will get it through the dedicated power connectors.  If you really want to you can buy the cable from cablesaurus that injects power using a molex connector into the pci express extension cable.

First, it probably isnt worth paying additional 50 euro per slot + riser. If you decide to go that route you have to use powered extenders (~$22 at cablesaurus, around half of that done by some forum member I think, $3-4 if bought in bulk from China). But even then I wouldn't bother, especially if those mobos don't have an 8-pin EPS12V connector. They aren't designed to supply so much power through all pcie slots and you risk frying you motherboard, maybe even the GPU(s) can get hurt. While using a powered riser definitely decreases the risk it makes it even more unprofitable. I wouldn't bother unless I could buy that adapter and a powered extender for $20-30 in total.

I will give you 5BTC if you can get your mining rig struck by lightning, and capture a picture of it.

Just sayin...

Okay, these replies are confusing me. Phorensic's implies that I do NOT need a powered extender (if the card need not get power through the slot, it need not get power through a powered extender either, surely?). Then malevolent says 'you have to use powered extenders'. Well, which one of you is right? Does my extender need to be powered or not?

If I DO get a powered extender, I'm not quite sure why malevolent says it risks frying my motherboard. Powered extender means no power from the mobo, right? I connect it directly to the PSU with one of its 4-pin molex cables for peripherals, don't I?

To clarify, I am only doing this for a SINGLE PCI slot. The adapter could be either PCIe x1 or x16 size... I have since seen cheaper adapters than that 50 euro one, but they only offer x1 size. I would prefer the x16, IF the extender need not be powered AND the motherboard will be safe, because I already have an unpowered x16 extender. OTOH if I need to get a powered extender, since I'll have to buy that separately I may as well make it a x1 to x16 extender and buy one of the cheaper x1 adapters.

If you do decide to invest money into making use of you PCI slot definitely use a powered extender. Doesn't matter if it's x1-x1, x16-x1, x1-x16 or some other, power comes only from x1 pins:
http://en.wikipedia.org/wiki/PCI_Express#Pinout

Why powered extender?
AFAIK PCI slot can give max. 25W
PCI-E - 75W

Doesn't mean it won't work, only it is safer to use a powered extender.

OK thanks this is much clearer than before. I have gone ahead and bought a PCI->PCIe-x16 adapter, turns out there was a cheaper one around that some guy posted in the general mining forum. That cost me $30, or about £20, which I'm happy to pay to stick another 5970 on Frankenstein. The 5970 in question is also on its way.

So that just leaves the question of the riser. Unpowered, already got. Powered, from cablesaurus (thx for that link) is about $27 including shipping. I have a bit of time to decide (if the 5970 comes early I stick it in my 'classy' miner which I have named Sisyphus). If the PCI can safely deliver 25W that gives the card a total of 250W to play with. I'm pretty sure my existing cards don't use that much. I only OC to 800MHz, 1.05V (can possibly get away with 1.04V) and mem 220MHz. My wall power draw is 1160W for four cards, which includes not one but TWO motherboards (+cpu+ram+usb stick for each) so I should be alright. But I might check the power draw of the components separately to make sure. I could always undervolt that one a bit.