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PCIE 3.0 16x or 8x

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May 5, 2012 6:52:13 AM

Would I notice much difference in performance if I had 2 gtx 680s in SLI on a mobo with 2 16x slots or 2 8x slots?
Currently debating over Gigabyte UD5H and Gigabyte G1 Sniper3.

More about : pcie 16x

a b V Motherboard
May 5, 2012 7:02:42 AM

not sure if both are in 16x 16x combo, but i remember reading that the difference between 16x/4x and 8x/8x are minimal fps
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May 5, 2012 7:07:17 AM

Well the G1 Snipers3 can run 16x/16x/0x/0x, 16x/8x/0x/8x or 8x/8x/8x/8x.
I was thinking that 16x/16x was unnecessary but just wanted a second opinion.
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Anonymous
a b V Motherboard
May 5, 2012 7:24:48 AM

even though i doubt it will matter, why risk any performance hit?
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a c 716 V Motherboard
May 5, 2012 11:38:12 AM

Skerbey said:
Would I notice much difference in performance if I had 2 gtx 680s in SLI on a mobo with 2 16x slots or 2 8x slots?
Currently debating over Gigabyte UD5H and Gigabyte G1 Sniper3.

Short answer is no. The only tests that I've seen where there's ANY differences between PCIe 2.0 x8 and even PCIe 3.0 x8 are in 4-WAY SLI of the GTX 680 AND with >5760x1080 (6.2+MP) resolution i.e. close to 4K 3840x2160 (8.3 MP). Meaning if you have a 30" (2560x1600) or HD (1920x1080) even 4-WAY SLI GTX 680's won't be effected even with PCIe 2.0 x8.
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May 5, 2012 4:17:29 PM

Anonymous said:
even though i doubt it will matter, why risk any performance hit?


Because the sniper is $200 more without wifi and worse integrated audio.

Quote:
Short answer is no. The only tests that I've seen where there's ANY differences between PCIe 2.0 x8 and even PCIe 3.0 x8 are in 4-WAY SLI of the GTX 680 AND with >5760x1080 (6.2+MP) resolution i.e. close to 4K 3840x2160 (8.3 MP). Meaning if you have a 30" (2560x1600) or HD (1920x1080) even 4-WAY SLI GTX 680's won't be effected even with PCIe 2.0 x8.


I thought as much. I'll be going with 5760x1080 2-WAY SLI GTX 680's so that should be fine.
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a b V Motherboard
May 5, 2012 4:45:07 PM

8x/8x is fine even for pci-e 2.0. With pci-e 3.0, 8x/8x has double the bandwidth of 8x/8x in pci-e 2.0.
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Anonymous
a b V Motherboard
May 5, 2012 5:09:20 PM

Skerbey said:
Because the sniper is $200 more without wifi and worse integrated audio.


oh, didn't realize that. go for x8/x8 then.
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a c 716 V Motherboard
May 5, 2012 5:18:39 PM

Skerbey said:
I thought as much. I'll be going with 5760x1080 2-WAY SLI GTX 680's so that should be fine.

First, NEVER use Wi-Fi on a desktop PC so either CAT-5e/6 or PowerLine. Wi-Fi is too laggy and bandwidth is like a bouncing bunny.

IMO SLI GTX 680's is barely enough for 5760x1080 especially if you want high details and forget 3D. Here's some good info:

TH SLI GTX 680's - http://www.tomshardware.com/reviews/geforce-gtx-690-ben...
TT 4GB GTX 680 (my choice with 3-WAY) - http://www.tweaktown.com/reviews/4665/palit_jetstream_g...
EVGA forum thread - http://www.evga.com/forums/tm.aspx?m=1537816
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May 6, 2012 3:08:49 AM

Ok, I'm confused about some of these resolutions. Where would one be using 2560x1600 or even 5760x1080? Are these 60 inch plasma televisions?
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a b V Motherboard
May 6, 2012 3:13:41 AM

therealsamyG said:
Ok, I'm confused about some of these resolutions. Where would one be using 2560x1600 or even 5760x1080? Are these 60 inch plasma televisions?


multple screens in eyefinity mode sorta like this
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a c 137 V Motherboard
May 6, 2012 4:03:34 AM

therealsamyG said:
Ok, I'm confused about some of these resolutions. Where would one be using 2560x1600 or even 5760x1080? Are these 60 inch plasma televisions?


2560x1600 is the native res of a 30 in. LCD monitor, and dudewitbow is right about the 5760x1080 being for multiple screens (3 in that case).
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May 6, 2012 8:46:00 AM

jaquith said:
First, NEVER use Wi-Fi on a desktop PC so either CAT-5e/6 or PowerLine. Wi-Fi is too laggy and bandwidth is like a bouncing bunny.

IMO SLI GTX 680's is barely enough for 5760x1080 especially if you want high details and forget 3D. Here's some good info:

TH SLI GTX 680's - http://www.tomshardware.com/reviews/geforce-gtx-690-ben...
TT 4GB GTX 680 (my choice with 3-WAY) - http://www.tweaktown.com/reviews/4665/palit_jetstream_g...
EVGA forum thread - http://www.evga.com/forums/tm.aspx?m=1537816


Barely enough? SLI GTX 680's play most games at 5760x1080 max settings with an average of 60 fps or more and minimum over 30 at least which is playable. I know minimum fps over 60 fps would be ideal but with a third card the gains are less significant as with adding the second. Still... if you're going all the way might as well go all the way. I might start with 2 cards and see how I go.

I'm not going to even bother with 3D. I don't really like it. Just makes my eyes hurt. It's a bit of a gimmick.

As for 4GB 680 cards I don't really see any significant advantage to the extra memory. A decent cooler will do you better.
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a c 716 V Motherboard
May 6, 2012 11:57:36 AM

therealsamyG said:
Ok, I'm confused about some of these resolutions. Where would one be using 2560x1600 or even 5760x1080? Are these 60 inch plasma televisions?

Depends entirely on the 'resolution' of the monitor(s) not it's diagonal 'size', but most "TV's" are 1080p (1920x1080) and the 'size' of the screen doesn't matter. Example an iPad 3 has more pixels (2048x1536) that your 60" plasma TV (1920x1080). From my examples 2560x1600 resolution is typically found on a 30" monitor and 5760x1080 is (3) HD monitors 'linked' together; (linking) nVidia calls it Surround and AMD(ATI) Eyefinity.

Skerbey said:
Barely enough? SLI GTX 680's play most games at 5760x1080 max settings with an average of 60 fps or more and minimum over 30 at least which is playable. I know minimum fps over 60 fps would be ideal but with a third card the gains are less significant as with adding the second. Still... if you're going all the way might as well go all the way. I might start with 2 cards and see how I go.

I'm not going to even bother with 3D. I don't really like it. Just makes my eyes hurt. It's a bit of a gimmick.

As for 4GB 680 cards I don't really see any significant advantage to the extra memory. A decent cooler will do you better.

The problem with 5760x1080 resolution is often enough a 'vRAM Bottleneck' and with 2GB of vRAM on plenty enough games with AA you'll be hitting a little as 5~8FPS. On a 30" @ 2560x1600 I haven't seen vRAM bottlenecks with any recent GTX 500 or GTX 600 series.

I've been running 3D Vision, (2D), and 5900x1080 (bezel correction) you do whatever fancies yourself, I'm only warning you. In 'my' case I'm (today) leaning towards SLI GTX 690's or maybe 4GB 3-WAY GTX 680's to replace the GPUs on our gaming rig, and I've done the research.

It's your rig - do the research. More than likely you'll need to look at forum threads like the one I posted above.

Good Luck!
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May 6, 2012 5:01:12 PM

jaquith said:
Depends entirely on the 'resolution' of the monitor(s) not it's diagonal 'size', but most "TV's" are 1080p (1920x1080) and the 'size' of the screen doesn't matter. Example an iPad 3 has more pixels (2048x1536) that your 60" plasma TV (1920x1080). From my examples 2560x1600 resolution is typically found on a 30" monitor and 5760x1080 is (3) HD monitors 'linked' together; (linking) nVidia calls it Surround and AMD(ATI) Eyefinity.


The problem with 5760x1080 resolution is often enough a 'vRAM Bottleneck' and with 2GB of vRAM on plenty enough games with AA you'll be hitting a little as 5~8FPS. On a 30" @ 2560x1600 I haven't seen vRAM bottlenecks with any recent GTX 500 or GTX 600 series.

I've been running 3D Vision, (2D), and 5900x1080 (bezel correction) you do whatever fancies yourself, I'm only warning you. In 'my' case I'm (today) leaning towards SLI GTX 690's or maybe 4GB 3-WAY GTX 680's to replace the GPUs on our gaming rig, and I've done the research.

It's your rig - do the research. More than likely you'll need to look at forum threads like the one I posted above.

Good Luck!


Thanks for your input. It's my understanding that a decent proportion of games are playable on at 5760x1080 on SLI GTX 680's except a few which can't handle AA or max settings but these are the few games that people are testing their rigs with. Still if all I need to do is put up with no AA on those few titles that's not too bad. Still have a bit of research to put in though. Hopefully by the time I'm ready to buy a better model has come out.

Those links you put up were good. I was able to see in some of the benchmarks that the min fps were significantly lower than the average fps. So I can see your concern for two cards not being enough.

What setup do you have for your current 5900x1080 display?
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a c 716 V Motherboard
May 6, 2012 6:09:31 PM

My rigs are listed under Member configuration, essentially the 5760x1080 (5900x1080 bezel correction) is from (3) Acer GD235HZbid 120Hz (3D) monitors with 3-WAY OC'ed GTX 470's. It's been under-powered for some time and I don't want a vRAM nor rendering problem GPUs. Today if I had to buy 'new' 120Hz monitors they'd have LightBoost; nice link - http://www.nvidia.com/object/3d-vision-system-requireme...

Remember, my (daughters) gaming rig is a couple years old. I 'can' accept replacing the GPUs + water blocks <or> EVGA Hydro Copper's, but not replacing the CPU (i7-980X), RAM, MOBO, and MOBO block. * So I 'get' money and some level of 'acceptable' loss from sacrifices.

I found out TH article is a little misleading as I expected it was which is why I researched a little more today, the GTX 690's are 2GB vRAM limited. The GTX 690 is essentially an SLI GTX 680 2GB ... so I'm back to waiting for 3-WAY 4GB GTX 680's.
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May 9, 2012 7:51:55 AM

Yeah its a decent comparison but a few of the games are processor bound so that gives the lower bandwidth slots more of a chance but the end results shows that for non processor bound games performance is somewhat proportion to the bandwidth i.e. PCIE 3 x8 ~ PCIE 2 x16. But we are still a bit off saturating the ports.
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a c 716 V Motherboard
May 9, 2012 12:03:06 PM

Skerbey said:
But we are still a bit off saturating the ports.

Hmm...the reason I posted the EVGA forum thread - http://www.evga.com/forums/tm.aspx?m=1537816 link is because they clearly were saturating the PCIe 2.0 x8 lanes with the GTX 680; keep in mind that was 5760x1080 with very high details and higher AA -- the images that are 'missing' showed the differences which were significant. However, it also required 4-WAY GTX 680's.

If your post was about PCIe 3.0 with 1920x1080 then none of this would apply.
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May 9, 2012 4:20:32 PM

I see. Well the test I linked was testing one card at the different speeds. What I think is happening in the test on the evga forum is that all 4 cards are trying to transfer data through the first cards PCIE rather than spreading the load across the 4 PCIE connections. those 4 cards have a combined 20 Gb/s i/o on PCIE2 and i dont expect they are utilising all of it. It is tested in an X79 platform which doesn't officially support PCIE3 for GTX 680's. I would like to see more 4-way set ups on Z77.
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a c 716 V Motherboard
May 9, 2012 7:59:32 PM

Skerbey said:
It is tested in an X79 platform which doesn't officially support PCIE3 for GTX 680's. I would like to see more 4-way set ups on Z77.

The ONLY PCIe 3.0 GPU that has any issues running PCIe 3.0 is the GTX 680. Chris did a review on the GTX 690 which does run PCIe 3.0 on the X79, and Chris is doing a new review as we speak on the GTX 670.

GTX 690 (i7-3960X + Gigabyte X79-UD5) IMO nVidia has some explaining to do - http://www.tomshardware.com/reviews/geforce-gtx-690-ben...


The Z77; 16 lanes PCIe 3.0 = 32 lanes of PCIe 2.0 so at least from a bandwidth point of view (worst case) it's the same. PLX chip simply has to funnel down to the same physical limits to the IB CPU.

Again, the ONLY GPU that has any issue is the nVidia GTX 680 - period; ALL others so far can and do run PCIe 3.0 on the SB-E -- further you can modify the registry values so even the GTX 680 run PCIe 3.0 on the SB-E.
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