Q: Will mining on a GeForce 750 Ti be bottlenecked by a PCI-E 1x slot? A: Yes!

D

dderidex

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For those wondering...

Ran a few hours of testing with a new GeForce 750 Ti on two different slots on my mobo. Same cudaminer config, same (slight) overclock.

In a PCI-E 16x slot that runs at 1x, the card was averaging ~200 khash/s. I did try a LOT of different configurations for this, overclocks, etc. Even pushed the video memory overclock up a few hundred mhz, which started to get me bumping into ~210 khash/s, although it did occasionally still drop below 200.

Same card in the PCI-E 16x slot that runs at 8x (split with the main GPU - it's an older mobo), and I'm at 300 khash/s.

So...there ya go. 8 times as many PCI-E channels for a 50% increase in output. (I'd presume this means I don't actually need the full 8 channels, though. As this 16x/1x slot on the mobo CAN be configured to run at 4x, if I disable my actually-1x-for-real slots, as well as USB 3.0 and 2 of the 6 SATA channels...I may ultimately do that if I ever decide to decommission this as my main gaming system.)

Anyway - food for thought!
 
Doesn't effect AMD cards running @ x1 vs x16, perhaps this is an Nvidia driver implementation issue?
 
atp1916 said:
Doesn't effect AMD cards running @ x1 vs x16, perhaps this is an Nvidia driver implementation issue?
Click to expand...

The 750 Ti draws its power directly from the PCI-E slot, could that be the issue here?

Well except for the EVGA model with the ACX cooler, that has a six-pin connector. Would be interesting to know if that card exhibits the same behavior.
 
atp1916 said:
Doesn't effect AMD cards running @ x1 vs x16, perhaps this is an Nvidia driver implementation issue?
Click to expand...

Huh - that's definitely odd, then.

Could be mobo, video card, nVidia drivers, cudaminer, or CUDA even, I suppose...
 
x3sphere said:
The 750 Ti draws its power directly from the PCI-E slot, could that be the issue here?
Click to expand...

Not sure - the slot is a full "16x"-sized slot, it's just the channels that are limited to 1x (or 4x, if I disable half my onboard stuff). I suppose it's POSSIBLE that Asus didn't connect all the power pins on it, but...seems somewhat unlikely? And the card is reporting the same clock speeds in EVGA Precision X before and after the move.

On the other hand, looking at the vCore on that card in the hardware monitor...it's a HECK of a lot more stable in the 8x slot vs the 1x/4x slot. You may be on to something...

Would definitely be curious to see if the cards with external power are not influenced by that.
 
Yeah I finally got my 5x GTX750ti system running last night and it is running 1450ish kH/s at 420w from the wall.

All the cards are within +- 5kH/s.

I suspect that it is a power issue as well. I am using a Asrock H81 BTC pro so it has extra power connectors on the board for feeding the pci-e slots. So in my case I am not using powered risers since board handles this.
 
I am curious about the ease of installation with the drivers, as in no problems seeing / installing cards etc?
 
The AsRock Pro BTC boards always confuse me since they have the molex power directly on the mobo. If using risers, does the power transfer through the 1x connection (USB or ribbon in this case) or do the risers still need to be plugged in? Both?
 
edge929 said:
The AsRock Pro BTC boards always confuse me since they have the molex power directly on the mobo. If using risers, does the power transfer through the 1x connection (USB or ribbon in this case) or do the risers still need to be plugged in? Both?
Click to expand...

you're supposed to be able to use unpowered risers with it but you'd probably be safer just using powered risers, unpowered risers may have more interference.
 
edge929 said:
The AsRock Pro BTC boards always confuse me since they have the molex power directly on the mobo. If using risers, does the power transfer through the 1x connection (USB or ribbon in this case) or do the risers still need to be plugged in? Both?
Click to expand...

On BTC series of boards you need to use unpowered ribbon risers since they have all the pins for the power.

If you are using usb style risers I think they have to be power since I don't believe there is enough pins in the usb connectors for both data, ground and power.
 
OP almost gave me a heart attack considering I have seven 750 Ti on the way. I'm going to be running them all via USB risers (PCB at each end, USB cable transfers data between, power to card-side PCB via molex 4-pin).

Guess we'll know for sure in about a week.
 
crspyjohn said:
It looks like a power issue.
Click to expand...

I think that's the take-away we are getting from this - as the card doesn't have a power adapter on its own (for most models), you MUST have a powered riser to ensure it gets enough juice to work properly.
 
dderidex said:
I think that's the take-away we are getting from this - as the card doesn't have a power adapter on its own (for most models), you MUST have a powered riser to ensure it gets enough juice to work properly.
Click to expand...
So, just to cross our Is and dot our Ts, can you please confirm explicitly that you were running yours on an unpowered 1x riser?

--H
 
draksia said:
Yeah I finally got my 5x GTX750ti system running last night and it is running 1450ish kH/s at 420w from the wall.

All the cards are within +- 5kH/s.

I suspect that it is a power issue as well. I am using a Asrock H81 BTC pro so it has extra power connectors on the board for feeding the pci-e slots. So in my case I am not using powered risers since board handles this.
Click to expand...

3.452 kh/w. That's amazing. If you aren't going for all out kh/s and are shooting for a more efficient design, Maxwell might be it. My R9 systems are somewhere in the range of 2.4-2.8 kh/w.
 
Hurin said:
So, just to cross our Is and dot our Ts, can you please confirm explicitly that you were running yours on an unpowered 1x riser?
Click to expand...

I wasn't running it on a riser at all, but off a mobo slot. So, theoretically, it *should* have received the power it needed.

However, watching the vCore bouncing around a lot more than it did when it was on a 'proper' 16x/8x slot (vs 16x/1x), I'm willing to believe the issue was lack of power. Asus cheaped out on the slot design or something.

The question is really what numbers people are hitting on their setups. When I put it in an 16x/8x slot, I'm seeing 300 khash/s pretty easily. When I had it in my 16x(kinda)/1x slot, I was at 200 khash/s. Sooooo...if other folks are getting the card up to 300 khash/s in a 1x riser, that says "power issue".
 
_r2h said:
3.452 kh/w. That's amazing. If you aren't going for all out kh/s and are shooting for a more efficient design, Maxwell might be it. My R9 systems are somewhere in the range of 2.4-2.8 kh/w.
Click to expand...
Yep. I ordered seven 750 Ti as soon as my calculations showed that I'd be making substantially more with four of them vs my two R9-290s. Power cost is $.32 per KWhr here. So it makes a substantial difference. Then I threw in three more because I was feeling greedy. :D
 
Hurin said:
Yep. I ordered seven 750 Ti as soon as my calculations showed that I'd be making substantially more with four of them vs my two R9-290s. Power cost is $.32 per KWhr here. So it makes a substantial difference. Then I threw in three more because I was feeling greedy. :D
Click to expand...

What hash were you getting on your 290s? Yeah, if my power was that expensive ($0.08 kw/h) I would definitely swap them out with Maxwell.
 
BallaTheFeared said:
I was under the impression that a standard x1 slot could only provide at max 25w of power.
Click to expand...

It's a mobo slot that is, in format, an 16x slot. Currently, it's running at 1x channels, although I can switch a BIOS setting to have it run at 4x (disabling half my onboard stuff to do so).

So I'd assume it would be wired for power for AT LEAST the 4x spec...but maybe ASUS has the 4x power pins disabled when the 4x data pins are?
 
edge929 said:
What hash were you getting on your 290s? Yeah, if my power was that expensive ($0.08 kw/h) I would definitely swap them out with Maxwell.
Click to expand...
I get 800 on one. 850 on the other.

WU is about 1510, generally. Power draw at the wall is 750w. But that's with an X58 and i920. The Haswell-T and mobo on the way should bring that down a bit too.

Incidentally, my power isn't that expensive until I use enough of it to get into the highest tier. Which, running 750w 24/7 obviously happens pretty quickly. Those who use less will pay less.

P.S. I'll be selling my Powercolor 290 w/ Accelero III. It runs incredibly cool and very quiet with the Accelero. Even at full hash, the VRMs don't get above 80c while the GPU stays around 65c (if memory serves). Paid $499 for the card and $85 for the cooler. Hoping to just get that back (w/out tax, obviously).
 
I've been thinking of selling my amd miners to get more of these 750s... i get better hash rate and like half the power usage... seems like a win/win. Sell those cards while they are worth something, I feel like in a month or two the big daddy maxwell chips will will drop, and will just eat AMD alive on power efficency/ hashrate ratios... if true it will really turn the tables.
 
jbean7457 said:
I've been thinking of selling my amd miners to get more of these 750s... i get better hash rate and like half the power usage... seems like a win/win. Sell those cards while they are worth something, I feel like in a month or two the big daddy maxwell chips will will drop, and will just eat AMD alive on power efficency/ hashrate ratios... if true it will really turn the tables.
Click to expand...

Yeah I've been mulling this too. It all depends on the bigger Maxwell chip efficiency. Right now the 750Ti is a little better than most AMD offerings, save for some golden samples. Most likely they will be better than AMD chips judging by the 750Ti. My biggest problem is that I would need at least three 750 Ti's just to match one of my 290s in hash power. That's 2 extra PCIe slots. If the ASRock PRO BTC boards were actually in stock at $70 a pop then it wouldn't be as big of an issue.
 
jbean7457 said:
I've been thinking of selling my amd miners to get more of these 750s... i get better hash rate and like half the power usage... seems like a win/win. Sell those cards while they are worth something, I feel like in a month or two the big daddy maxwell chips will will drop, and will just eat AMD alive on power efficency/ hashrate ratios... if true it will really turn the tables.
Click to expand...

Yeah I have 3 R9 280x's that just eat power. The question is get more 750ti's or wait for a bigger Maxwell.

650w 80+ gold or better and 750ti's would definitely be nicer on the power and ac bill.
 
The prospect of bigger Maxwells later is why I'm not skimping on the power supply right now (silly Thermaltake 1200W needs replaced because it's not single rail and only has 20A on the rail going to molex connectors-->risers).

The only downside I'm anticipating with the Maxwell conversion is the lack of polish in the mining environment. I'm going to miss cgwatcher (etc.).
 
Hurin said:
The prospect of bigger Maxwells later is why I'm not skimping on the power supply right now (silly Thermaltake 1200W needs replaced because it's not single rail and only has 20A on the rail going to molex connectors-->risers).

The only downside I'm anticipating with the Maxwell conversion is the lack of polish in the mining environment. I'm going to miss cgwatcher (etc.).
Click to expand...

It will only be a matter of time before those things pop up for the nv side... but intially it will be like "roughing it" a bit...
 
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