I'm pretty sure mine are drawing closer to 60 watts when crunching flat out, as I recall that when I replaced a GT 640 with an EVGA 750Ti (in September, 2014), my power use went up by 4-5 watts, instead of going down by about that amount, as I had expected. I also just replaced a passively-cooled GT 630 (very low power usage) with a PNY 750Ti several days ago, and the draw increased by about 45-50 watts.

Did you check the older cards, and the current GTX 750Ti, with GPU-Z (or similar) to see what the load on the cards was/is?

As far as GPU Load goes on the 2 older cards, I've generally been able to keep them at about 92-98%. Under S@h v7, that was running 2 tasks at a time, but with v8, it initially dropped into the mid-80s, so then I switched to 3 at a time. Now, with the VLARs on GPUs, I don't know where I'm at, so I'll have to check it all again some time. I haven't, however, checked the load on the new card yet, and I don't think I've ever paid attention to what the Max TDP percent was. I just used my Kill-A-Watt to check changes in total wattage used.

I don't think I've ever paid attention to what the Max TDP percent was. I just used my Kill-A-Watt to check changes in total wattage used.

It would be interesting to see just how the GPU-Z % of max TDP values and the Kill-A-Watt readings compare.
My UPS gives me load readings, but they vary depending on whether it's on mains power or battery. And even then it gives the load in 13W increments. Not very useful.
:-/

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Grant
Darwin NT

I don't think I've ever paid attention to what the Max TDP percent was. I just used my Kill-A-Watt to check changes in total wattage used.

It would be interesting to see just how the GPU-Z % of max TDP values and the Kill-A-Watt readings compare.
My UPS gives me load readings, but they vary depending on whether it's on mains power or battery. And even then it gives the load in 13W increments. Not very useful.
:-/

Yeah, I'd probably have to swap cards in and out to do that kind of comparison, so not something likely to happen. When I'm replacing a card, I usually just take a Kill-A-Watt reading before and after. For instance, on the recent replacement of the GT630 with the GTX750Ti on host 6949656, under the GT630 configuration the host was using ~139-144W total, while the initial reading on the GTX750Ti configuration showed ~182-191W total, in both cases only running 1 task at a time on the GPU. Bumping that up to 2 tasks at a time on the 750Ti didn't seem to change the power usage that much, but the range widened slightly, to ~178-195W total.

If I think of it later, I'll check the current max TDP when that box starts back up again this evening. (All my crunch-only machines take a 5 hour break starting in late afternoon, to avoid the "peak period" electric rates.) I'll probably also check where the GPU Load is at, and whether or not increasing to 3 at a time makes sense on that host. Even with rescheduling as many VLARs to the CPU as the two cores can reasonably handle, the GPU is still having to crunch an awful lot of those suckers.

I have GTX 750Ti SC. Single fan. No external power connector. So it gets all the power from PCI-e slot.

Mine does not report watts. I use MSI Afterburner and GPU-z, neither show power usage in watts. It does report percentage. I have not seen it go higher than 70%, usually it stays in low 60%.

If I recall, PCI-e is rated for 75 Watt?
So 60% of 75 Watt is 45 Watt.

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If I recall, PCI-e is rated for 75 Watt?
So 60% of 75 Watt is 45 Watt.

That's the maximum rating for the slot, according to the EVGA page the card is rated for 60W maximum. So it'd be closer to 36W.

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Grant
Darwin NT

Okay, I just looked at the GPU-Z numbers for all 3 of my 750Tis and can't relate them to much of anything. The PNY that I just installed on 6949656 showed an average GPU Load of 99% running one guppi VLAR and one non-VLAR, with a power range of 35.1% to 65.9% TDP. When the VLAR finished and a non-VLAR took its place, the GPU Load dropped to 96% and the power increased to a range of 53.5% to 71.9%.

On my host 6980751 which has two 750Tis (both EVGA, but with different base clocks) and two GTX 660s, each of which is running 3 tasks at a time (which happen to all be non-VLARs at the moment), one 750Ti has a GPU Load of 86%, with power ranging from 48.6% to 71.7% TDP. The other has a GPU Load of 85%, with power ranging from 40.0% to 71.7% TDP.

Bottom line.....I have no idea what that's all really telling me. ;^)

Bottom line.....I have no idea what that's all really telling me. ;^)

Maximum power usage is around 72% of the maximum possible, so around 43W according to GPU-Z.

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Grant
Darwin NT

Bottom line.....I have no idea what that's all really telling me. ;^)

Maximum power usage is around 72% of the maximum possible, so around 43W according to GPU-Z.

Yeah, but that's inconsistent with what Kill-A-Watt was showing me, where just the increase in power usage from the previous GT630 card to the GTX750Ti was in the 39-51W range. So, even if the GT630 was only using, say, 15 watts, the total for the 750Ti would be in the 54-66W range. I suspect that some of these factory-overclocked cards actually consume more power than the reference wattage that NVIDIA provides.

Oh, well, I mainly just care about the total wattage for each box and what that does to my electric bill, which I'll think about another day. It's past this old man's bedtime. ;^)

Overclocked cards will almost inevitably draw more power than reference cards.

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Bob Smith
Member of Seti PIPPS (Pluto is a Planet Protest Society)
Somewhere in the (un)known Universe?

Been running With USB riser for a while now, and the Cards are running stable on the riser. Haven't had any problems With the Cards or Power Connectors.

I think the danger of shorts With the USB riser are lower than With ribbon risers.
To avoid any danger of differential voltage when running With multiple Power supply, i would recommend connecting the 0 volt line from each Power together.

Been running With USB riser for a while now, and the Cards are running stable on the riser. Haven't had any problems With the Cards or Power Connectors.

I think the danger of shorts With the USB riser are lower than With ribbon risers.
To avoid any danger of differential voltage when running With multiple Power supply, i would recommend connecting the 0 volt line from each Power together.

Very good advice.
I have never run a multi PSU setup. I have opted instead to overkill with single rail PSUs.
But, I have never tried to front more GPUs on a rig than one PSU could handle.
There is a point where that becomes fruitless, because the mobo infrastructure breaks down and adding more GPU power loses it's impact.

Better to construct another rig and give the GPUs the support they deserve.

Meow.

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"Freedom is just Chaos, with better lighting." Alan Dean Foster

Well, the reason I am asking about these is that I am putting together One. Last. System., and it is going to be an interesting one. Similar to both my CrunchMonster and LotzaCores systems, in that like my CrunchMonster it is going to be a multi GPU setup, and like my LotzaCores system, it will be based upon a Supermicro motherboard, this time a X10DRX dual proc board. What makes this one interesting, is that it has ten 8x PCI-E slots, and the plan is to (eventually, as finances allow) utilize all 10 of them using the USB-PCI adapters. My goal is to use the 750Ti SC cards, which do not require external power, with a 1600w PSU.

The biggest thing I believe I need to worry about is properly distributing the power for those adapters, because I'm pretty sure it will be easy to overload those Molex/SATA power cables off of the PSU, considering that they were pretty much designed for floppy or DVD drives, not something sucking up 150-225+ watts...

If they don't have enough connections/cables, I will see if I can locate any 6 or 8 pin to Molex/SATA power adapters. Not sure if they are even made or not, or if they actually supply the proper voltage thru them for those USB adapters. Just thought of that off the top of my head, will def need to do more research while assembling it. Should be interesting though! :-)

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Well, the reason I am asking about these is that I am putting together One. Last. System., and it is going to be an interesting one. Similar to both my CrunchMonster and LotzaCores systems, in that like my CrunchMonster it is going to be a multi GPU setup, and like my LotzaCores system, it will be based upon a Supermicro motherboard, this time a X10DRX dual proc board. What makes this one interesting, is that it has ten 8x PCI-E slots, and the plan is to (eventually, as finances allow) utilize all 10 of them using the USB-PCI adapters. My goal is to use the 750Ti SC cards, which do not require external power, with a 1600w PSU.

The biggest thing I believe I need to worry about is properly distributing the power for those adapters, because I'm pretty sure it will be easy to overload those Molex/SATA power cables off of the PSU, considering that they were pretty much designed for floppy or DVD drives, not something sucking up 150-225+ watts...

If they don't have enough connections/cables, I will see if I can locate any 6 or 8 pin to Molex/SATA power adapters. Not sure if they are even made or not, or if they actually supply the proper voltage thru them for those USB adapters. Just thought of that off the top of my head, will def need to do more research while assembling it. Should be interesting though! :-)

The cards may not require external power, but how about the copper wires on motherboard and the connections leading to them: Can they supply?

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To overcome Heisenbergs:
"You can't always get what you want / but if you try sometimes you just might find / you get what you need." -- Rolling Stones

The cards may not require external power, but how about the copper wires on motherboard and the connections leading to them: Can they supply?

Good point.

From the PCIe Wiki

All ×1 cards are initially 10 W; full-height cards may configure themselves as 'high-power' to reach 25 W, while half-height ×1 cards are fixed at 10 W.
All sizes of ×4 and ×8 PCI Express cards are allowed a maximum power consumption of 25 W.
All sizes of ×16 cards are initially 25 W; like ×1 cards, half-height cards are limited to this number while full-height cards may increase their power after configuration. They can use up to 75 W (3.3 V × 3 A + 12 V × 5.5 A), though the specification demands that the higher-power configuration be used for graphics cards only, while cards of other purposes are to remain at 25 W.[12][13]

Optional connectors add 75 W (6-pin) or 150 W (8-pin) power for up to 300 W total (2×75 W + 1×150 W).
Some cards are using two 8-pin connectors, but this has not been standardized yet, therefore such cards must not carry the official PCI Express logo. This configuration would allow 375 W total (1×75 W + 2×150 W) and will likely be standardized by PCI-SIG with the PCI Express 4.0 standard.

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Grant
Darwin NT

Hmm, interesting, but I believe that the power is actually supplied by the Molex connection, not thru the USB cable, correct? So in reality, no power is being drawn thru the PCI-E bus, because it is going thru a USB cable, which is a very low power connection. The 1x is just transferring the data, not the power, unless I have the concept of these cables wrong. But I have read of numerous people using these to run remote from the MB video cards for mining, so I can't imagine that there is an issue with what I am planning? Or am I missing something. I would love to know before I start putting things together, I can always change course at this point. Let me know your thoughts, thanks!

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Hmm, interesting, but I believe that the power is actually supplied by the Molex connection, not thru the USB cable, correct? So in reality, no power is being drawn thru the PCI-E bus, because it is going thru a USB cable, which is a very low power connection. The 1x is just transferring the data, not the power, unless I have the concept of these cables wrong.

Depends how it is wired, but i'd expect they'd have to supply some power.
Pins 1-3 and 8-10 all supply power on one or more of the pins (Side A or B of the slot).
So i'd say any cards that have an Aux PCIe power connecter would be OK as most of the power should be supplied through them, but any boards without an aux PCIe power connector would likely overload the PCIe *1 slot.

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Grant
Darwin NT

Any difference that this is a 8x slot? I know it's not a 16x, but maybe it will be enough? Hmm... Maybe I should look at the 750Ti FTW, which I believe has 2 fans and a 6 pin connector? Only slightly faster, and little more expensive, but if it's a solution...? I suppose I can try running one or 2 of the non-powered Ti's first and see if there are any unusual issues during testing.

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Looking at the pinout for the PCIe connectors, there are no additional power pins over what is in the PCIe*1 slot.
PCIe *4, *8 & *16 slots only have additional data, ground & presence pins. There are no additional power pins.

So even though PCIe *1, *4 & *8 are limited to 25W maximum according to the specification, the 75W available to a *16 device is supplied by the same pins that supply the *1 slot power.

The presence of a *16 card may result in a current limit to that slot on the power supply to it being lifted. But that's just speculation.


From the looks of things, the PCIe *1 is capable of supplying 75W, however without the presence of a high power *1 device, or a *4 or * or *16 device in the slot the output may be limited to as little as 10W if the manufacturer follows the spec.

The issues will be- can the card get more than 25W (or even 10W) from the slot?
If it can, just how much capacity does the motherboard have?
If there are 10 PCIe*1 slots, and the maximum for PCIe*1 is 25W then the total power across all the slots may be only 250W, which is about 4* 60W cards (without aux PCIe power connectors).

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Grant
Darwin NT

Well, I pulled up the manual for it, and on 2-7 (49th page) it lists:

Chapter 2: Installation

2-7 Connecting Cables

Power Connectors
A 24-pin main power supply connector
(JPWR1), two 8-pin CPU power con-
nectors (JPWR2/JPWR3), and a 4-pin
Auxiliary power connector (JPWR4) are
located on the motherboard. These power
connectors meet the SSI EPS 12V speci-
fication and must be connected to your
power supply to provide adequate power
to the system. See the tables on the right
for pin definitions.


Looking at the picture of the board on the 10th page, it has stickers covering those two 8 pin connectors, saying "Both 8 pin required for heavy load configuration". I guess I don't know if those are supplying additional power for the CPU's, or the PCI-E slots. I believe the chart next to that 2-7 text says 12v though.

In the specs at the beginning of the manual, it says:

Expansion Slots

• Ten (10) PCI-Express 3.0x8 slots (CPU1 PCI-E Slot1-Slot5, CPU2 Slot6-Slot10);
• One (1) PCI-Express 2.0x4 in x8 slot (CPU2 Slot 11);
• Slot1-Slot8 are open-ended.

Not sure if any of this helps at all, but this it most of the info I found regarding power, and the PCI-E in the manual. There are a few diagrams that may have information about it, like on page 18 (1-10), but someone more knowledgeable than I would have to decipher it.

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Bottom line.....I have no idea what that's all really telling me. ;^)

Maximum power usage is around 72% of the maximum possible, so around 43W according to GPU-Z.

Yeah, but that's inconsistent with what Kill-A-Watt was showing me, where just the increase in power usage from the previous GT630 card to the GTX750Ti was in the 39-51W range. So, even if the GT630 was only using, say, 15 watts, the total for the 750Ti would be in the 54-66W range. I suspect that some of these factory-overclocked cards actually consume more power than the reference wattage that NVIDIA provides.

Oh, well, I mainly just care about the total wattage for each box and what that does to my electric bill, which I'll think about another day. It's past this old man's bedtime. ;^)

https://www.overclockers.co.uk/evga-geforce-gtx-750ti-ftw-acx-2048mb-gddr5-pci-express-graphics-card-02g-p4-3757-kr-gx-242-ea.html

Not sure if you have the FTW ACX version , but that seems to suggest that is up to 120W as a theoretical maximum, whereas

https://www.overclockers.co.uk/msi-geforce-gtx-750ti-low-profile-2048mb-gddr5-pci-express-graphics-card-n750-ti-2gd5tlp-gx-32t-ms.html has 60W

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