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Author Topic: Are cards on PCIe extenders less stable or is my power too low?  (Read 2060 times)
El Cabron
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November 28, 2011, 11:59:35 AM
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I have a rig running 2 5850s in their normal slots and 1 5830 on a PCIe 1x to 16x extender. The hash rate goes from about 249MHash/S to 277MHash/S, up and down quickly. The 5850s are stable, never change more than 1Mhash/S.

Is the problem the extender or should I be looking at something else?

Also ideas on how to fix it?

Thanks.

Edit:  Just realized my PSU on this is a 650W. This might be why? Most of my other cards on the extenders are fine.

Thx

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deslok
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November 29, 2011, 03:52:35 AM
 #2

the amperage on the 12v rail is more important than overall wattage when building a mining rig (volts*amps=watts so a 5830 needs 15a and a 5770 needs 9 for example) check your total 12v amperage and if it's a multi rail psu make sure you're not loading one rail and leaving the other empty.

as far as risers making things less stable since PCIe wasn't designed with long distances in mind it is possible, expecially with longer risers towards the furthest slot on the board or if you have other sources of emf(ex wires running between cards) present

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anatolikostis
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December 12, 2011, 02:40:10 PM
 #3

I`ve got a several 5850/5870 on a PCIe 1x to 1x extender witn no problem in using, but I`m not minning now...
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December 12, 2011, 03:34:40 PM
 #4

Sure not.

chungenhung
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January 11, 2012, 02:43:48 AM
 #5

it should not, as it will get the needed power from the two 6pin plugs.
Your 650w power supply might not have enough power for all 3 cards.

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January 11, 2012, 04:05:12 AM
 #6

chungenhung is right...  get yourself a good PSU.

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jake262144
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January 11, 2012, 09:24:50 AM
 #7

Just realized my PSU on this is a 650W. This might be why? Most of my other cards on the extenders are fine.

Goat, PSUs aren't made equal.
Wattage specified on the label is next to useless.
A PSU built on an old-design might give you 250W on +3.3V and +5V rails and only 400W on +12V rail.

A decent DC-to-DC PSU can easily supply you with 630W of that sweet 12 volt juice as long as you don't draw too much power from +3.3 and +5 volt rails.

What's the make and model of that PSU of yours?
Also, take a good glance at the load chart. It's right there on the side you your PSU.
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January 11, 2012, 12:37:11 PM
 #8

The TX series has been manufactured for  Corsair by Channel Well Technologies (CWT), unlike TX v2 (check the model number) which is being made by Seasonic.
This is a common problem with PSU brands: the same brand and wattage doesn't mean the internals are the same or even made by the same manufacturer.

The TX seres uses DC-to-DC conversion and should give you 620 Watts at the +12 rail.
Of course, part of that +12 power is being consumed by the CPU, fans, and drives. The other rails (3.3 and 5v, often called minor rails) are of course also being utilized by the rig, lowering the amount of current you can draw from +12 lines.

I wasn't able to fine overload tests for this exact model but is bigger brother (tx750) has been successfully overloaded by 20% (a total of 900 Watts on the DC side) at the cost of increased power noise and ripple.

You wouldn't have an electricity usage monitor (a popular brand is Kill-A-Watt) lying around?
IMO every serious miner should have on for determining and fine tuning the power consumption of their rigs.
Maybe grab some knock-off from e-bay?

Or, you could give me the details of your rig and we'll try to assess the idle power consumption and thus - how much juice this baby can pump into the cards.

Links (if you're interested in the technicalities):
   This is how a proper PSU review is made:
      http://www.hardwaresecrets.com/article/Corsair-TX750W-Power-Supply-Review/505/1
      http://www.jonnyguru.com/modules.php?name=NDReviews&op=Story&reid=254
      http://www.jonnyguru.com/modules.php?name=NDReviews&op=Story&reid=230
      http://www.jonnyguru.com/modules.php?name=NDReviews&op=Story&reid=73
   Unlike this:
      http://extreme.outervision.com/articles/psu/corsair/tx650/corsair_tx_650_1.jsp
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January 11, 2012, 01:55:36 PM
 #9

500W at the outlet? That's just 410W at the DC side assuming 82% efficiency. Yeah, you should have plenty of headroom. I wouldn't expect the 6770 to use more than 120W, even overclocked.
Have fun with it!
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January 12, 2012, 10:24:51 AM
 #10

Basically... nope. Marginal riser cables don't cause hashrate fluctuations, they do cause hard lockups and/or cards sometimes not getting recognized on boot.
On a similar note marginal power doesn't cause hashrate fluctuations either, it causes hard lockups and crashes.
What os/driver/sdk/miner combo?

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Chefnet
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January 12, 2012, 12:45:08 PM
 #11

my 2x5970 pull out with each 720 - 780 mh/s on pcie x1 and pci to pcie to pcie x1 (clocke 150/800).
I dont know what you are doing wrong maybe it is the psu.

Chefnet
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January 12, 2012, 02:39:55 PM
 #12

yes I can with adapters pci to pcie :-)

If you need some you can buy them from me, I have a small buisness in Germany.

jake262144
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January 12, 2012, 03:09:34 PM
 #13

Those would be POWERED pci to pcie extenders of course, Chefnet?

The spec allows up to 75W for pci-e but no more than 25W for good-old pci. Supplying external power is therefore mandatory.
Just wanted to bring this potential point of failure to attention.
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January 12, 2012, 03:21:14 PM
 #14

hi

thx for advice.

the pci is not extra powered, but the extender on it (I use x1 >x16 normally) are with extra power molex.

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