Quote from: rahrahrah on February 28, 2014, 09:59:39 PM

Quote from: gfgrimm on February 28, 2014, 08:49:42 PM

I've now got 6 750 Ti's running on Win8 x64. I'm pretty disappointed.

1 Cards, OC'd, in x16 slot (running at x16): 320-330 kH/s [Total of 320-330 kH/s]
2 Cards, OC'd, in 2 x16 slots (each running at x8): 300 kH/s each [Total of ~600KH/s]
4 Cards, OC'd, running on x1-x16 risers (each running at x1): ~270-280 each [Total of ~1100 kH/s]
6 Cards, stock, running on x1-x16 risers (each running at x1): 230-240 each (one runs at ~210 and is operating at PCIe 1.1 x1...whereas all the other cards are running at PCIe 2.0 x1) [Total of ~1430kH/s]

I haven't been able to get 7 Cards to show up in Windows...figure that it could be a MoBo/BIOS address space limitation.

I can't really apply any overclock at all when I have 6 cards loaded. MSI AB, GPU-Z, etc., all feel a little unstable when using. Applying even just +100MHz to MEMCLK will cause cudaminer to crash.

I have also noticed that my little G3220 is way too puny to run -H 1 flag.

Here are the flags I'm running -H 2 -i 0 -l T25x16

Will I see improved scaling in Ubuntu with cudaminer?

I'm thinking of returning all of these cards because 230 kH/s per card is not so great. If I was even hitting 280, I'd maybe be able to swallow this.

What is the primary factor here causing a scalability issue? Is it the PCIe operating mode? Is it Windows 8? Is it the Nvidia Driver? Is cudaminer not written to scale well past 4 GPUs?

Yes, I did try running 2 or 4 cards each in a separate cudaminer instance. While the system stability improved, the results yielded the same aggregate hash rate, and any attempts to boost any clocks cause a quick cudaminer crash.

If I can't get more out of these cards by Monday, I'll have to send them back to Newegg. Sad

Am I misunderstanding something? With:

1 Cards, OC'd, in x16 slot (running at x16): 320-330 kH/s [Total of 320-330 kH/s]
2 Cards, OC'd, in 2 x16 slots (each running at x8): 300 kH/s each [Total of ~600KH/s]
4 Cards, OC'd, running on x1-x16 risers (each running at x1): ~270-280 each [Total of ~1100 kH/s]

That's 7 cards (with OC) at best case 292KH/s ave, or 285KH/s ave? More than the 280 you said you might be able to swallow? Are you factoring in power usage into your valuation of the cards? It seems they use even less than first thought.

I've got 5 x Gigabyte 750 Ti waiting to plug into a Win 7 x64 system but I need risers before I get going, so I'm very interested in the experiences and thoughts of yourself and j0achim (and indeed any others with 5+ cards in a single rig!).

You do misunderstand. Each line is a different configuration to track the scalability of performance--I tried 1 card, 2 cards, 4 cards, and then 6 cards. The performance I listed above is what I got.

The degradation of performance and overclockability seems to be linear with the # of cards plugged in at once...