First Impressions From a 6-card Mining Rig using GeForce GTX 750 Ti GPUs

7 Mar
2014

six-gpu-rig-gigabyte-geforce-gtx-750-ti

Today we have built a 6-card mining rig using Gigabyte GeForce GTX 750 Ti (N75TOC-2GI) video cards that are based on the latest Nvidia Maxwell architecture promising very good performance for mining with low power usage. Our own initial tests of the GeForce GTX 750 Ti as a single card for mining have shown very promising results as well, so we’ve decided to see what we can expect from a mining rig and put together 6 cards with PCI-E x1-x1 extenders on an AsRock H81 Pro BTC motherboard with Intel Celeron G1820 CPU and 4GB of RAM running Windows 7.

six-gpu-rig-gigabyte-geforce-gtx-750-ti-hashrate

The result we’ve got from the 6-card mining rig for mining Scrypt with CUDAminer was a total of 1480 KHS as hashrate. Then after overclocking the video cards to the maximum stable result we managed to get (+135 MHz for the GPU and +610 MHz for the video memory) we’ve managed to increase the total hashrate to about 1615 KHS. We went as far as to increase the power target limit from the default 38.5W by modifying the video BIOS of the cards. With the modified video BIOS we have managed to get slightly more than 1700 KHS with a lot of extra power used by the whole system that made it not worth it the so little extra increase in the hashrate. Just to be sure that the x1-x1 PCI-E risers (not powered) might be the cause of slight performance drop we’ve replaced them with x1-x16 USB 3.0 powered extenders, though that did not change the performance we got from the cards.

The Gigabyte GeForce GTX 750 Ti video cards we used for the mining rig do have an external PCI-E power connector, however it seems that unlike AMD graphics with OpenCL, when using Nvidia-based GPUs with CUDA for mining the use of a x1 PCI-E lane to access the video card does introduce slight performance drop and if you multiply the 10-15 KHS less per card for a 6-card mining rig it is not so little. So it is important to know that if you are going to build a GTX 750 Ti-based mining rig you will be getting slightly lower hashrate if you are using PCI-E extenders as compared to what you will get with cards inserted in x16 PCI-E slot directly. Also there is some variation between cards in terms of the maximum overclock supported that results in different maximum frequencies that you can achieve, for example if one card is able to do +135/+700 MHz for the GPU/VRAM the second one could be maximum +100/+600. This means that in a 6-card mining rig you will need to either sync all of the cards and use the same lower settings for overclocking the GPUs to ensure they will run stable or to not have the settings synced and find the maximum for each of the cards.

Another interesting thing we have noticed is that while the use of T5x24 kernel for a single card with CUDAminer for best results, for a 6-card mining rig the use of T10x24 might sometimes provide slightly higher hashrate than T5x24, so you should try with both and see what works better in your individual case. Tomorrow we are going to be doing some more testing of the 6-card GTX 750 Ti mining rig that will be focused mostly on the power consumption as this is also a very important thing when talking about crypto currency mining.



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33 Responses to First Impressions From a 6-card Mining Rig using GeForce GTX 750 Ti GPUs

Anders

March 8th, 2014 at 17:24

Hi!
I am greatly enjoying your insightful blog! Keep up the good work.
Like you I am also interested in the new GTX 750 Ti :)
Would you be so kind as to measure what the Total System Power draw is for the above system? (measured from the wall).

Do you know/think that the performance hit from putting the 750ti in a 1x slot (or riser) can be negated if you have a motherboard with 6x pci-e x16 slots – AND using (if they even exist???) x16 – x16 risers??? I am asking as i have a spare P6T6 ws revo board with 6x pci-e x16 slots that could be used then :D

admin

March 8th, 2014 at 22:17

Anders, we are soon going to publish another article about the power usage of the mining rig above.
With all cards on true x16 PCI-E slots there should be no performance drop like with the use of x1 PCI-E risers.

Henrik

March 9th, 2014 at 03:29

Hi

Me and a friend are building a similar setup, we also use 6 cards with PCI-E x1-x16 extenders on an AsRock H81 Pro BTC
Cards are Gainward 750 Ti.

We have a problem with detecting more than 4 cards in windows, we have tried windows 8.1 and windows 7.

I feel like we have tried almost everything, different BIOS versions, switched the cards arround, tested the raisers (we found one bad). We also tried to put one of the cards directly in the x16 slot.

Sometimes windows detects 4 cards, sometimes 3 or 2, but no more. (device manager)

All the cards are working, 5 of the risers have no problems.

The risers are powered so power to the cards is not an issue (when 4 cards is detected they all work good)

Did you just plug the cards in and it worked?

We have been trying to figure out the problem for 3-4 days now, could the motherboard be bad maybe?

Wired thing is that when we switch around the risers on the motherboard some pci-e ports works sometimes, and other times not. Almost seems like windows detects 3 or 4 cards and skips the rest (in random order).

Is there something we have missed?

Thanks
-Henrik

Oriumpor

March 9th, 2014 at 04:28

Henrik: You need powered USB risers, and make sure you’re balancing the power across the rails. (multiple channels) I’m using the SATA style power connectors for 3 and the molex connectors for the other three.

It’s not that you *might* not have enough power on the motherboard (even with that additional molex connector) you won’t. You need at least 2 rails (probably 3) to get enough wattage to the cards.

The problems I experience with this config (I’m pushing roughly 1450kh/s) is that there’s no real management of the cudaminer config. You’ve gotta run Windows 7/8, you’ve gotta tweak it to autologin/autostart since Cuda needs the context of an explorer shell that’s using an actual cuda adapter, and there’s no RPC/decent logging.

I’ve got it working with a keystick and WinToUsb, but Cudaminer is trying to swap to disk and causing the system to prompt to kill the app (it’s still running) since there’s no swap on a usb image.

Being able to pull 1450kh/s on a low power config is great, being able to manage, reboot, log or check temperature would be on par with the AMD support on CGminer. Nvidia’s SMI supports temperature at least, which would be a nice add.

Honestly Cudaminer just needs some love.

Henrik

March 9th, 2014 at 06:57

Oriumpor: Thank you for the reply. Power is not an issue in this rig, all the risers are powered.

The issue we are having is no more than 4 cards are detected by Windows (In device manager)

It works perfectly with the 4 detected cards, but would be nice to be able to use the last 2 cards :)

Thanks
-Henrik

admin

March 9th, 2014 at 11:01

Henrik, we did not have problems with Windows 7 detecting and running cudaminer on all 6 cards.
Check all of your individual risers and cards one by one in order to ensure they all work fine, we’ve had a bad riser when setting up things, but after replacing it all worked just fine with all 6 cards.

Aurosonic

March 9th, 2014 at 13:48

here is my setup for 1800 khs with 6xMSi 750Ti TF:

– ASRock H81 pro btc with 1.50 bios update
– PSU Corsair CS750M 750W
– DDR-III 8GB Corsair 9-9-9-24 1333Mhz
– SSD Sandisk 60GB
– 6x MSI 750Ti Twin Frozer with following settings:

all cards bios modded to 66.5W Powerlimit
All cards overclocked to +135/+520 except 1 card ( it lacks with just +135/+300 )
Each card plugged to mb with powered usb 3.0 risers 1m lenght.
Overall power consumption is 555-565W.
All the temps are less than 60.

my cudaminer setting: -i 0 -H 2 -l T10x24 -m 1 -b 4096

you have to use x86 cudaminer + google chrome with some flash animation for best results.

http://i.imgur.com/MHZxZsA.png

http://i.imgur.com/J8edxuB.jpg

http://i.imgur.com/nHboH4p.jpg

Henrik

March 9th, 2014 at 22:28

Aurosonic:
Thanks for the reply :)

Our conclusion is that there must be something wrong with the motherboard or with normal powered raisers, the usb 3.0 raisers look so much better.

Nice setup btw, just watch out for static electricity from that carpet, i would recommend you to at least put some cardboard or other non conductive material under your usb 3.0 riser units :)

-Henrik

RavenX

March 10th, 2014 at 01:36

Hi,

Awesome blog with awesome info… keep it up!!!

1) Supposing a rig with 3 GTX 750 Ti (Gigabyte versions), which PSU and MOBO do you suggest?

2) You guys are using Intel MOBO/Processor. I heard that GTX 750 Ti is not very “friend” of AMD ones. What you think about it?

Regards… ;-)

admin

March 10th, 2014 at 02:40

RavenX, for a three card mining rig there are many options for motherboards and you don’t need a much powerful PSU either. You can probably even find some good motherboards with three x16 PCI-E slots so you don’t have to use PCI-E risers and will be able to get the maximum performance oout of the cards (x1 raisers do lead to some slight drop in performance). A good 400-500W PSU should do the job great, the GTX 750 Ti are not power hungrly cards :)

We are using AsRock’s motherboards that are designed for crypto mining rigs (Pro BTC series), because they are a great choice for motherboard for 6-card mining rigs, not only for AMD GPUs, but for Nvidia as well. We have used and tested a GTX 750 Ti on an motherboard designed for AMD processors and had no trouble at all, we got pretty much the same performance as on an Intel-based motherboard.

RavenX

March 10th, 2014 at 04:31

Thanks for the reply.

I´m totally newbie on this “coin” world (just one week with deep research) and doubts are always on my mind. Thus, having such help is very good.

I live in Brazil and, looking in a very good local retailer, found these parts that I think are good for the project and have a good price:
– GPU: 3 x Gigabyte GeForce GTX750 Ti OC GV-N75TOC-2GI
– PSU: Corsair ATX 12V/2.3 430W CMPSU-430CXV2
– MOBO: GigaByte p/ Intel GA-H61M-S1 LGA1155
– CPU: Intel Celeron G1610 2.6Ghz 2M Cache LGA1155 – BX80637G1610
– RAM: Kingston 4096 MB (4GB) 1333Mhz DDR3 CL9 – KVR13N9S8/4
– HDD: will try to find some old one with some friend… :-P

I was afraid of chosing this MOBO(http://br.gigabyte.com/products/product-page.aspx?pid=4127#sp) because it has “mixed” PCI-e slots:
– 1 x PCI Express x16 slot, running at x16 (The PCI Express x16 slot conforms to PCI Express 3.0 standard.)
– 2 x PCI Express x1 slots (All PCI Express x1 slots conform to PCI Express 2.0 standard.)

But I noticed that the board you mentioned in the post (AsRock H81 Pro BTC) has:
– 1 x PCIe 2.0 x16
– 5 x PCIe 2.0 x1

So, my afraid was gone… :-)

What do you think about the parts I mentioned?
It’ll be enough?
Some of them are not good (quality regarding)?

Another doubt:
If I would like to start with 1 GPU (money is short) and then add more with time, is there any problem?

Last one:
Can I have one GPU directly plugged on the PCI-e x16 and the other 2 with risers?

Thanks in advance… ;-)

admin

March 10th, 2014 at 15:22

RavenX, the AsRock Pro BTC motherboards we often use are specially designed for mining rigs with more cards.

In your case you need less PCI-E slots available (note that for x1 slots you will need to use extenders), and you can also look for motherboards with three x16 PCI-E slots (even if physical some of them are wired at x4 or x4) as with Nvidia GPUs the use of x1 extenders leads to some slight drop in performance. So if you want to get the most out of the cards look for a suitable motherboard with large PCIE slots that will allow you to put all three cards directly on the motherboard.

The motherboard from Guigabyte you have chooses should be good for three cards, and you can start with one and add the other two after that with extenders… no need to use powered extenders with the GTX 750 cards you have chosen. If you plan on going all the way up to 6 cards, then the AsRock Pro BTC motherboard will allow you to do it. The power supply should be more than enough for 3 cards, though you might go for a bit more powerful like 600W model if you consider going up to a 6-card setup later on.

RavenX

March 10th, 2014 at 17:22

After a thorough research this night, I bought one Gigabyte GeForce GTX750 Ti OC GV-N75TOC-2GI.

For me now, the best option is to replace my GTS450 with it:
– 3~4 times more KHs
– half GPU power consumption
– minimum money spent

After I get used with it, and have more money, maybe I start to build a rig.

Thx again for the support… :-)

Charlie

March 10th, 2014 at 21:19

First off, thank you so much for this blog. Trying to find info on running the gtx 750 tis or even just nvidia mining has been a pain with all the posts dedicated to amd mining.

I’m curious about hooking up 3+ cards. I bought 5 evga FTW gtx 750 ti cards and have only been able to get windows to recognize 3 of them. I have an array of risers to try (some x16, some x1, some with molex connectors, some unpowered) and it doesn’t seem like any combination gets me more than 3 operable cards.

I checked every card and riser by booting with only 1 card plugged in and all worked fine. I even tried different (though not all) combinations of 3 cards in 3 different pcie slots. All worked just fine.

Currently I have three x1 powered risers and two x16 powered risers connecting the cards to the mobo (gigabyte, GA-990FXA-UD3). On boot up, I can see 3 cards in device manager, gpu-z, and evga precision X. Windows also runs hardware set up for two instances of “nVidia High Definition Audio Device.” I guess there’s something goofy somewhere that won’t allow the cards to be recognized as gpus, but as sound cards?

Any thought would be welcome and much appreciated. I have some extra risers that I could modify to take 12V power off of a different source (not molex) if you think that would fix things.

admin

March 10th, 2014 at 22:38

Charlie, this motherboard might not be able to provide enough power to 5 video cards, try with powered risers. Also check what configuration do the slots on the motherboard support, the four x16 slots should be able to take cards, but the two smaller x1 slots might not be working if you have cards in all of the x16 slots. Check the manual of the motherboard for more information about the PCI-E slots.

Charlie

March 12th, 2014 at 03:39

Ok, so now I’m getting windows to recognize all 5. Here’s what I did:

Installed the newest nVidia driver. I had the newest up until a few days ago when they released a new one, so I’m not that much of a noob. This resulted in windows seeing 4 cards.

I swapped out the riser on the card that was not showing up. This riser works when there are 3 or fewer cards plugged in, but a friend told me to try it. So I replaced the powered x16 riser with an unpowered x1 riser I had lying around. That did the trick. I am now mining with 5 cards.

Still toying with settings in evga precision X, but I’m just happy all the cards I spent money on being productive.

by the way, I have a sixth card on order and the only unused slot at this point is a pcie x16 slot so I’m hoping I won’t have any issues, but we’ll see

RavenX

March 12th, 2014 at 03:53

If I’m not blind, the six GPUs are using the 6 pin power conector, right?

Could you guys please give more details about the “power part” of the system:
Are you using a single PSU?
Which model?
Which cables from PSU are being used?

Thanks in advance.

RavenX

March 12th, 2014 at 06:55

Do you guys see any problem on using de the AsRock H61 Pro BTC MOBO instead of H81?

They are cheaper and also the processor.

admin

March 12th, 2014 at 10:32

RavenX, the GTX 750 Ti cards are not so power hungry, so no problem using a not so powerful PSU and using molex to PCI-E power. We are using a 750W PSU, but it is way more than needed. The H61 should also be Ok, it depends on what you have available at the moment, we did not have H61, so we used H81 motherboard.

Jonatan

March 12th, 2014 at 14:24

Excellent review, very useful. I bought 1x MSI 750Ti Twin Frozer and 1x Gigabyte GeForce GTX 750 Ti (N75TOC-2GI) to test first if there was any real difference, and it looks like MSI handles better OC than Gigabyte, so I’ll return the Gigabyte and get 5 more MSI.

I want to get a H61 as the mobo, but I’m not sure if a Celeron G470 would be enough. I would be using -H 2, but still, using 6x GPUs, what is the CPU usage of your G1820 from your test? (or if anyone else could leave info about their CPU usage…)

Thanks!

admin

March 12th, 2014 at 15:05

Jonatan, The CPU usage is very low with the -H 2 option, so there should be not problems even with a slower CPU.

RavenX

March 12th, 2014 at 20:39

Thx for the info.

Do you use those adapters with 2 molex conectors on one side and 1 PCI-E on the other?
Or those with 1 on each side?

Sorry if the questions look so “noob”.
I’m really new to this.

;-)

admin

March 12th, 2014 at 21:01

RavenX, the mining rig above was built using non-powered PCI-E extenders as the video cards do have PCI-E power connectors on them. For powered PCI-E risers we like to use the ones that use USB 3.0 cables as they are much better quality than the ribbon models that have the molex for power attached to them.

Charlie

March 13th, 2014 at 20:03

Update:
I have 6 cards running. It will only allow for one x16 riser connected card. When I try more than that, windows does not recognize it. I assume that’s a mobo issue, but I’m not certain. The other 5 cards are on x1 risers. Some are powered, some are not. This does not seem to matter as I have a friend using all un-powered ones. All cards are connected to the psu using the 6-pin pcie/vga power cables.

The card on the x16 riser is doing 10-25 KH/s better than the others. I’ve gotten this result even when I’ve switched risers and which card is hooked up to an x16.

I haven’t done individual card tuning yet, but I have them at +50 gpu clock, +450 memclock and am getting 1760 KH/s stable. Still want to play with it some and see if I can coax 1800 out of it.

Rig specs:
GPU: 6x EVGA GTX750TI FTW
CPU: AMD Sempron 145 2.8GHz AM3
MOBO: Gigabyte GA-990FXA-UD3 Rev 4.0
PSU: EVGA SuperNOVA NEX 650Watts

Admins, I do have a question for you. You mentioned that the T5x24 config worked best for one card, but the T10x24 config worked best for 6. Any reason to believe that running 6 instances of cudaminer (using the -d tag to only use one card per instance) at T5x24 would be beneficial?

admin

March 13th, 2014 at 20:57

Charlie, the reason why the to kernel configurations work in different condition probably has to do with the fact that the single card uses PCI-E x16 directly and the 6-card rig uses risers that do introduce some slight performance loss, so apparently T10x24 does perform better when using risers. You should however try both to see what works best in your case.

RavenX

March 14th, 2014 at 00:32

Ok, one more noob question.. =P

The video cards have PCI-E power connectors on them and you are powering through it. That’s clear.
Do your PSU have six independent cables with 6 PIN connector? Or you use adapters on other cables coming from it?

Looking at mine PSU right now (a modular one), I have one cable with the 6 PIN connector powering my GPU and can plug another.

Regards.

admin

March 14th, 2014 at 02:00

RavenX, no the PSU only has two 6-pin PCI-E power connectors, the other 4 are 4-pin molex to 6-pin PCI-e adapters.

RavenX

March 14th, 2014 at 06:15

Awesome, now it’s crystal clear to me.

Thank you very much for the info and patience… ;-)

NewMiner

March 20th, 2014 at 00:55

Have you tried running the same card powered through the 6-pin on board connector, and also just by a powered riser to try and get a sense of if it truly helps to power it directly or not?

So much unknown it seems, but with the availability of the cards and prices being $30-50 more for the twin fan/on board power it may or may not be worth it.

Thanks in advance if you are able to do some testing on this.

NoobMiner

March 30th, 2014 at 21:55

I’m a bit unsure about powering the GPUs and risers. Can anyone help? Would you have to power the GPU (Gigabyte GeForce GTX750 Ti OC GV-N75TOC-2GI) direct from the PSU if you’re using powered USB 3 risers? Or would the GPU take its power from the USB PCIE riser alone? Thanks in advance for helping.

I’ve ordered the following for my rig:

x 1 ASRock H81 Pro BTC Motherboard
x 6 GIGABYTE NVIDIA GTX 750Ti 2GB PCI-E Graphics Card
x6 MINEPRO POWERED USB3 PCIE PCI-E Riser Cable 1X to 16X
x 1 Kingston 120GB SSD
x 1 PSU EVGA 750W SuperNOVA NEX750G Gold
x1 Kingston Technology KHX1600C10D3B1/8G 8GB 1600MHz DDR3
x1 Intel CPU – Box (BX80646G1820)

admin

March 30th, 2014 at 22:38

With the Gigabyte cards if you have the PCI-E power connector connected to the video card you can go without powered risers, though the cards will works just fine with powered risers. Normally you would need to use powered risers if the cards you are using do not have external PCI-E power connectors on them.

Eric Ochoa

April 6th, 2014 at 07:04

I’m having similar issues. I am using the btc pro board, I am not connecting the molex power on the board. I am using 6x usb powered risers, and 6 of the gigabyte oc edition with dual fans. When I have only 4, everything is fine. Connect 5 or 6 and I get error 43, device won’t start. Going to swap out the risers first. Can you simply not connect the power on those and they will work as unpowered?

NoobMiner

April 6th, 2014 at 16:04

I’m having some issues with Cudaminer. I’m using Win8.1 with Cudaminer x86. x6 Gigabyte 750TIs. I’ve tried variations of the parameters in cudaminer, most of them resulting in this message “”Geforce GTX 750TI result does not validate on CPU”. Eventually, I did get it working, but it is hashing at an unbelievable 1.09 khash/s!

Here’s what I have got:

cudaminer –algo=scrypt:2048 –devices 0 -l T5x24 -i 1 -o stratum+tcp://stratum.simplevert.com:3343 -u VbCPGD1ieqV9mp9TDuNZhYAssZMwhDNYDc.worker1 -p x

What do you think I am doing wrong? Thanks in advance!

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