How big a rig is too big?

[joblo]

If you have more than 6 cards,you need powered risers . A 750ti draws 50-60 watt depending on what you mine. So a 16 cards rig will only draw around 1000W. The bios might need to be cracked to support 16 cards, and more than 8 cards in windows is a pain.  Have anyone tried 5 7990's in one single rig ? (10 gpu's)
You probobly need linux. Expensive PCIE splitters etc.

powered riser are useless if you have asrock h81 with two molex, i always used ribbon standard risers and they work fine for every card out there, also cost less than powered riser

I have to disagree. Although the mobo can supply the power cheap risers sometimes can't. At least with powered risers
you're not trying to push 75W through a ribbon wire. It also reduces the overall power going through the mobo. The cost
difference is trivial, no more than .05 BTC with risers on all 6 cards.

If using two PSUs (not my thing) I believe you need powered risers to isolate them.

average wattage per card today, especially with new nvidia is very low, they consume 150w on average, very low as i said they will use the 8 pin if not enough current come from the x1 slot, i think you don't need to provide 75w fromt he slot, lol future gpu with 10nm or less, will consume so low that not even a 6 or 8 pin would be required, only the riser

High end graphics will still need 2x8pin to consume total of 375W as they are more powerful cards.

To my knowledge 2x8 pin is not standard, and, IMO, won't be needed as power draw is dropping even as performance
increases. Top end GPUs will be engineered to require no more than 300W (slot+6+8).

For the AMD cards, the sapphire 280x uses 2x8pin, the 7990 uses 2x8pin, the R9 Fury also use 2x8pin.

the trend is to consume less for future gpu, so they will end up with only one 8 pin and then 6 pin eventually it's onyl a matter of time

in few generation you will have zero 6 or 8 pin needed for mainstream gpu, not for high end like 980ti or 390x
[/quote]

Agree mostly, but I think top end GPUs will continue to push performance within the power ceiling until one GPU can
do 4K@120 or more. But the days of triple slot and dual GPU cards that can heat a small house are over.

The 750ti set a new standard with no extra power connector. the 730, although Kepler, is also a trend setter as
a half length, half height card. The R9 Nano is another card that packs a lot of performance in a small energy
efficient pasckage. Pascal will set a new standard. AMD, well I hope they can at least keep up to keep Nvidia honest.

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[Bamsed]

If you have more than 6 cards,you need powered risers . A 750ti draws 50-60 watt depending on what you mine. So a 16 cards rig will only draw around 1000W. The bios might need to be cracked to support 16 cards, and more than 8 cards in windows is a pain.  Have anyone tried 5 7990's in one single rig ? (10 gpu's)
You probobly need linux. Expensive PCIE splitters etc.

powered riser are useless if you have asrock h81 with two molex, i always used ribbon standard risers and they work fine for every card out there, also cost less than powered riser

I have to disagree. Although the mobo can supply the power cheap risers sometimes can't. At least with powered risers
you're not trying to push 75W through a ribbon wire. It also reduces the overall power going through the mobo. The cost
difference is trivial, no more than .05 BTC with risers on all 6 cards.

If using two PSUs (not my thing) I believe you need powered risers to isolate them.

average wattage per card today, especially with new nvidia is very low, they consume 150w on average, very low as i said they will use the 8 pin if not enough current come from the x1 slot, i think you don't need to provide 75w fromt he slot, lol future gpu with 10nm or less, will consume so low that not even a 6 or 8 pin would be required, only the riser

High end graphics will still need 2x8pin to consume total of 375W as they are more powerful cards.

To my knowledge 2x8 pin is not standard, and, IMO, won't be needed as power draw is dropping even as performance
increases. Top end GPUs will be engineered to require no more than 300W (slot+6+8).

For the AMD cards, the sapphire 280x uses 2x8pin, the 7990 uses 2x8pin, the R9 Fury also use 2x8pin.

the trend is to consume less for future gpu, so they will end up with only one 8 pin and then 6 pin eventually it's only a matter of time

in few generation you will have zero 6 or 8 pin needed for mainstream gpu, not for high end like 980ti or 390x

People are greedy, they want high performance cards, that will use more power. Maybe the limit is around 400W.

[joblo]

the trend is to consume less for future gpu, so they will end up with only one 8 pin and then 6 pin eventually it's only a matter of time

in few generation you will have zero 6 or 8 pin needed for mainstream gpu, not for high end like 980ti or 390x

People are greedy, they want high performance cards, that will use more power. Maybe the limit is around 400W.

If they standardize 8+8 pin connectors that will give 375 but I doubt that will happen. Nvidia will never release a
GTX990  even though they could probably stay within the 300W limit. A 1080ti or 1090, or even a 1090ti  probably
wouldn't require 8+8 if the ever come to pass. The trend has been toward lower power, even at the top end, for
several years.

[Amph]

it must be said that at some point titan x and 1080ti would become the new meanstream if the consumption level will be very low for that, so it may be possible to assist to a new rank for gpu

[Tacalt]

But you look at AMD, they are using the water cooling for the 295x2 and Fury XT. That is happening.

[RoseMann]

In the future, maybe just the Dual GPU cards will consume 375W. All the single GPU cards will consume less than 200W.

[LadangGalau]

I've never found any affordable motherboard with more than 6 GPU PCI-E, so since 6 GPUs would be my answer.

[Docnaster]

I've never found any affordable motherboard with more than 6 GPU PCI-E, so since 6 GPUs would be my answer.

The MSI Z77A GD 55 or GD 65 have 7 PCIE slots and you can use all the slots. I used to own GD55. I bought it now $120, sold it second hand $150.

[RoseMann]

I've never found any affordable motherboard with more than 6 GPU PCI-E, so since 6 GPUs would be my answer.

The MSI Z77A GD 55 or GD 65 have 7 PCIE slots and you can use all the slots. I used to own GD55. I bought it now $120, sold it second hand $150.

These two boards are very robust. They both have onboard power switch and reset switch, so very convenient.

[Tacalt]

I've never found any affordable motherboard with more than 6 GPU PCI-E, so since 6 GPUs would be my answer.

It is better to use the 6 PCIE boards. They are more available. If any thing is wrong with one board, you can find a replacement easily.

[Docnaster]

I've never found any affordable motherboard with more than 6 GPU PCI-E, so since 6 GPUs would be my answer.

It is better to use the 6 PCIE boards. They are more available. If any thing is wrong with one board, you can find a replacement easily.

I used to use the Asrock H61 pro btc. They are all working well for over two years. I am building new rigs with the H81.