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Just a reminder to stay safe out there.  I just built a quad 7950 setup, spent ALLL DAY getting my settings so it worked just right...  and about an hour after I left it sit to mine...  mobo fire.  :o

Luckily it was very small and I was in the room so I was able to catch it as it happened / shut it off / make sure everything was ok.  I had the board on the bottom of the crate which was on a wood table, nothing able to touch the board that shouldn't have, and no extreme overclocking (just +7% power to the video cards).... I think I just got a defective board.  Has anyone else experienced this?

I got a bamboo cutting board today as an extra piece of insulation for the replacement motherboard to rest on, but it has me a little freaked out.  I may not want to run it when I can't be here to watch over it, at least for the first week or so.

Have you used powered risers?

No I was not.  2 of my cards were directly in 16x slots and the other 2 were on riser cables, I followed a guide I found online that made no mention of powered risers.... might be that I need to get a couple of those before I fire it back up

But I forgot to ask, were you mining LTC by chance?
For BTC mining should be no problem having 4 cards without powered risers.

Yes I was mining LTC, if I don't need powered ones for BTC than at least the ones I have aren't a complete waste

Can you give us a complete list of your hardware and temperatures before the fire if possible, also your mining/OC settings.

AMD Sempron cpu
ASRock 970 extreme3 Motherboard
8gb corsair / kingston RAM (w/ same clock settings / voltage)
4x sapphire 7950 (1100 core, 1500 mem, +7% power in catalyst), 2 on non powered 1x->16x risers and 2 on the motherboard
- guiminer scrypt with 7950 high usage defaults
Netgear USB wifi
HP wireless kb / mouse
small box fan

Fire was on the corner of the board near the psu input. Cards got as high as 80c, but I was playing with fan controls / box fan combo doing pretty well at keeping them in the 75-78 range

You were asking your board to deliver 300W+ of power. That 24pin is not rating to carry that much [well it is, but really pushing it], nor is the power delivery system within the motherboard.

Looks like power circuit mosfets caught the fire. Never use boards that have so low quality that even the manufacturer name is written with one S letter missing.

High-end boards have additional power connectors to additionally feed the PCI-E lanes. Most of them use floppy connectors placed near PCI-E slots.

I can't exchange the board for something else, I can only replace / refund it, and my replacement has already shipped.  It will be here tomorrow.  I have also ordered powered riser cables but they won't be here probably until sometime next week.

I also didn't note above, my psu is a seasonic gold plus 1250w

So should I ...

A) Rebuild this rig using the 1x->16x riser cables that have a molex connector for extra power on them

B) only run it with 2 video cards

C)??

A) Powered risers. (you don't need to have them all powered, two powered and two simple should do)

As a side note you can use this http://www.extreme.outervision.com/PSUEngine to calculate the power you need for your components.

Thanks for that looks like I went overkill on the psu....  I only needed a 750, but its the same power draw anyway, so mine just won't work as hard as a 750w would

I can always use it to rebuild a super fancy gaming pc one day  :)

Looks like I will be running this thing with just 2 cards starting tomorrow, and probably adding in the other 2 whenever my powered risers arrive.

Can anyone confirm that I don't need powered risers for btc mining?  Or should I just throw those non-powered risers in the junk parts bin?

remember that only 2 of the 4 cards were on risers, the other 2 were plugged directly into the 16x slots on the motherboard....

I did not see the pictures but according to description the PWM area / mosfets caught fire. Nothing to do with PCI-E lanes. ASSrock is making much better boards than they were few years ago but this happens from time to time. AM2+ boards combined with 6core black edition phenoms were prone to PWM failures with fire back then. And MSI and Gigabyte were best burning boards back then.

I mine BTC on one rig with 5 7970 cards without powered risers, just simple risers.
For BTC mining we usually down-clock the memory as low as we can go.

LTC mining OTOH is using high memory clocks and pulling a lot of power from the motherboard.

That is correct, those tiny chips near the 24 pin connector is what caught fire.  But how does that have nothing to do with the PCIe lanes?  I am no expert, just thinking that if the PCIe lanes were asking the board for more power than it could supply, it would make sense for the PWM area of the board to become overloaded / unstable / or in this case on fire, wouldn't it?

Thanks, so I can at least use the risers I have, though I probably won't unless I build a btc specific rig.

Something like this: https://bitcointalk.org/index.php?topic=161242.msg1703391#msg1703391 ?

Yep lol, that is my board and that is exactly where my fire started.  Notice he also was doing LTC without powered risers.... at least I know now, but I am still gonna be real scared to leave the rig running unattended after this.  Maybe I can set it up to run in my fireplace, just incase   :D

 ;D ;D ;D

These chips power the CPU that is the real power drawer from motherboard. Some AMD FX processors consume 140W and more when pushed really hard.

The cards take most of the power from additional power connectors from PSU. If the motherboard is unable to supply all PCI-E slots with nominal power it most likely will result in instability not fire. So I think the problem was low quality board components that gave up when put to use not configuration of the devices.

The GPUs are indeed drawing power from additionally cables, but the memory is still drawing power from PCI slots. (Issue amplified when mining LTC)
This, combined with low quality components will lead to melting cables or even fire.
A problem that powered risers can solve.

Interesting.... I was under the impression that the cpu would not be used when mining, so a rig just mining and doing nothing else wouldn't really put considerable use / stress on a cpu.

Anyway this thing was sitting not 3 feet from a large stone slab in front of my fireplace, which will be the new home for it when it gets rebuilt. It will have several days of mining under a watchful eye before I even think about leaving it.  I'm now wondering whether that bamboo board is a good idea or not, but maybe I will just get a nice (real) case with insane ventilation for it when the funds allow.

It is not.

and knowing is half the battle!
thanks for sharing

LOL right  :)

I got the new board today, am running it now with only the 2 cards in the provided 16x slots / no risers

The mosfets are still getting pretty hot to touch but no fires yet   ::)  Not sure how hot they are supposed to get / are rated for, I will probably go ahead and put all the cards on powered risers over the next week or 2 just to reduce the load on the motherboard

That stinks. Imagine if you hadn't been there:(. If I build a rig, I better not let my parents see this or that's a straight out no for me:). Hope you figure out the problem and it works out fine next time.

Thanks,  I watched it for a couple hours today and the mosfets got warm, not too hot to touch just warm, and it was stable with no issues.  So I am pretty sure it was the non-powered risers that caused the issue.  I will probably be ordering some more so all 4 cards will be on powered riser cables and that will keep the motherboard from struggling to provide power.

I was going to leave it as a crate rig but I may want to put it in a real case now that this incident has me paranoid about it.... anyone know of an atx case with 12+ back panel slots to properly space these cards??  lol

You can buy one of these, no problem leaving the house.

http://www.flyingarchitecture.com/wp-content/uploads/2010/03/fireplace2.jpg

LOL that might defeat the purpose  ;)

I know that back in the ancient times of about a decade ago when I was in college, a buddy of mine had built his pc into a large server tower that had TONS of extra slots / bays....  but I can't seem to find anything like that out there right now

No luck on a case, but I did find a rack that will probably suit my needs.  In the crate, video cards are staggered vertically so they touch each other at the corners, but fans have enough open space between them for good ventilation.  The rack I want to use would not give me as much vertical room.  So that brings me to another stupid question!

If I got my 2 powered risers, and had 2 cards on those with the other 2 cards directly in the 16x slots on the motherboard and it runs stable in that configuration.... Could I use one of my non-powered risers just to spread the cards out for better airflow?  Meaning I would have 2 cards on powered risers, one card in the motherboard 16x slot, and one non-powered 1x->16x riser in the other 16x slot for the last card.  I don't see how this would be any different for mining than having 2 cards directly on the motherboard, unless the 1x (non-powered) riser is not capable of transferring as much power as a regular 16x slot? Would this work? 

I could always just get another riser for the rack that I want to use, but I hate to waste the ones I already have.

quad GPU needs LOOOOT of cooling while in closed - case. I would personally build/buy open case for such rig

Oh where is Bitcoin Mining Accidents (https://twitter.com/BitcoinAccident/status/89769986171731968) when we need them (http://uberbills.com/bma-article.JPG)!  :-\

I'm runnin 3 7970s on unpowered risers through a 1200w FSP Group on a Gigabyte B75 board + Celeron g1610 combo with no problems mining ltc for roughly a month now...

OP, you never mentioned your PSU specs? Or maybe i'm blind... :o

With only 3 cards you should be reasonably safe. With more than 3 use powered risers.
Better safe than sorry, OP was running 4.

Ok.

Thanks  :)