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I currently have 4 cards (5830 + 3x5850) on an MSI 890FXA-GD65.  I am considering adding two additional 5850s.  I have two concerns:

1)  Can the MSI 890FXA-GD65 utilize all 6 PCIe ports simultaneously?  Is anybody running 6 cards>
2)  Should I be concerned about overloading the 12V rail on the motherboard?  Although most likely irrelevant, I will be running from 3x500W PSUs. Does anybody have any good sources for inexpensive PCIe extenders with molex connectors?

Any other thoughts are appreciated.

Dan

I have run 6 cards on the gd70, I dont have any gd65's.  I ran them for about a day or so, but I stick to 5 cards on each board.

I run 6x on the -70. Of course one the 65 you're going to need to split-molex the pci power.  But since I'm able to run 6x on the 70 without doing so, I'm going to guess you'll have no power related problems on the 65 with split pcie power.

Its just not a good idea, You need to run molexed adapters to take the 12v of the board. You will need to run a dual psu which just adds to what can go wrong. Also you will notice that with 6 cards that the system is just not stable. 5 is the max for the 58xx

Thanks, prof.

But I'm using PCI-E 16x extenders, and I'm (crazily enough) within pci power specs.

I am also completely stable, with 1950MH/s (on 5830s), 60 days uptime (since last power outage)  on quite a few systems.

Check your submited shares for me will you? That thing I saw was that they just didnt perform that well with 6 on that setup.

That hashrate is computed from the submitted shares over a ~three week period.  I don't trust the miner figures either: I've certainly seen cases where turning the overclock up lowered the share rate while raising the hashrate without showing any errors.

To be fair, I had some stability problems while I was running 2x950 PSU which went away when I switched to 950+1200 and switched to 240v (I didn't both at the same time so I don't know which to credit— the PSUs I tested _do_ manage to handle more load at 240v).  I've also noticed reduced performance from more GPUs but I found this was addressed by increasing the intensity and worksize.

(and without increasing stale rate in any meaningful way— .... now I'm mining using p2pool, which has a 10s merged blockchain for payout agreement, and my stale rate on it is much lower than typical)

just as an update...  I have extra cards now.  so I am running 6 vaporx 5870's on a gd70.  clocks 930/300 stable for 3 days now :) ~2550Mh

1 1200 watt silverstone for 4cards and the mobo
1 idontknowwatt for the other 2 cards

you can get a p6t7 and mine with 7 cards at once :p

Nope. Tried it, it bottlenecks. We tried it with 5770 and 5830s. Just no way around it. And even with 6 cards, most boards will not handle it well.

Most Ive seen was 8 via a pci -> pcie adapter.

Can the MSI Big Bang-Marshal run 8 HD5870s or 8 of any other card?
http://www.newegg.com/Product/Product.aspx?Item=N82E16813130595

Or is it better to run less then 6 cards per motherboard?

It may but people have indicated problems.  Given the relative cost of 5870s and 5970s and the huge cost of those 6,7,8 slot boards it simply makes more sense to run 4x5970s on a "normal" board.  With extenders even an entry level board w/ 1 PCIex16 and 3 PCIex1 slots is sufficient for ~3 GH/s.

my http://www.gigabyte.de/products/product-page.aspx?pid=3272#ov (http://www.gigabyte.de/products/product-page.aspx?pid=3272#ov) has 7 cards with pci - pcie adapters without problems :-)

I have successfully gotten 6 cards running on a MSI 890FXA-GD65.  I am using molex PCIe Extenders for two of the cards.  So far everything appears to be stable.  Thanks for your opinions on this.