2-way SLI on Maximus V Extreme - best slots 8x/8x or 8x/16x?

[feniks]

I am looking at ASUS MVE manual and it seems that for 2-way SLI ASUS proposes using Intel CPU native bandwidth for both cards (8x/8x natively) using slots PCIe3.0_1 (top first) and PCIe3.0_2B (third from top). I know that switches/bridges may cause some lag, so it makes sense *IF* each of cards doesn't exceed the PCIe3.0 8x bandwidth (I think 670 2GB cards don't but I am unsure of it).
Also this configuration allows for better air flow between cards which probably matters if one relies on air cooling ... I don't, both cards are water cooled.

however I see there is also another config possible which is based on 3-SLI configuration and for 2-SLI it would suggest using both top first and second slots, PCIe3.0_1 & PCIe3.0_2A respectively for x8/16x.

tomorrow I will be installing my second 670 2GB for 8x/8x config for now and I hope it works fine (no lag related to PLX chip switching).

does anybody have some benchmarks comparing same cards and CPU clock (and memory) running 2 cards in each of mentioned configurations?

Thanks!

[SUKARA]

By asus user manual page 1-26 described,i recommend that you can use 8x/8x
Because,asus for the SLI or AMD crossfire feature to test by slot PCIE 3.0/2.0/x8_1 & 2B
So,if not such a installation,will be does not guarantee the system run stable

[HiVizMan]

The cpu only has 16x capability. That is an Intel thing so end of any discussions on how to get more out of the system lanes.

Your performance will be totally unaffected with two cards at all. And if i am going to be perfectly blunt, unless you have a huge resolution screen or screens a single top end card like yours will not even be maxed out, never mind two. 🙂

So do not stress at all and just enjoy your system my friend.

[feniks]

SUKARA@ASUS wrote:
By asus user manual page 1-26 described,i recommend that you can use 8x/8x
Because,asus for the SLI or AMD crossfire feature to test by slot PCIE 3.0/2.0/x8_1 & 2B
So,if not such a installation,will be does not guarantee the system run stable

yeah, thanks. That's what I said initial post (quoted manual), because since ASUS tested the other pair of slots in 3-SLI I wondered if you guys considered running 2-SLI over it (one card straight to CPU other through the multiplexer PLX chip)? asking just of curiosity, since the issue is purely academical most likely as it is highly doubtful (I might be wrong) that the 670 (or 680 or even 690 for that matter) card could fill the 16x bandwidth of PCIe3.0.

HiVizMan wrote:
The cpu only has 16x capability. That is an Intel thing so end of any discussions on how to get more out of the system lanes.

Your performance will be totally unaffected with two cards at all. And if i am going to be perfectly blunt, unless you have a huge resolution screen or screens a single top end card like yours will not even be maxed out, never mind two. 🙂

So do not stress at all and just enjoy your system my friend.

Thanks.
I am aware how many native lanes the 1155 CPUs are capable of 🙂

asking purely because I have experience with running 570 cards in SLI on older boards via both the native lanes (slots assigned straight to CPU) or via slots assigned to multiplexer chip (PCIe2.0 NF200 on evga Z68 FTW or PCIe3.0 PLX PEX 8417 on evga Z77 FTW board).
when comparing native 8x/8x versus multiplexed 16x/16x the difference in benchmarking scores was around 5% in favor of multiplexed connection.
Since Maximus V Extreme carries 2 multiplexing chips and use of those slots assigned to them is required for 3- and 4-SLI setups for achieving the 8x/16/8x or 8x/16x/8x/8x configurations, I was wondering if ASUS or someone here tested the configuration of 8x/16x for 2-SLI and compared it directly to native 8x/8x just to see if there is any significant difference (or none) in benchmarking scores 😄

Of course it means probably nothing for 2-SLI over PCIe3.0 since the potential bandwidth is huge and it is doubtful 670 (or even 690 for that matter) cards fill it up to 16x each. as I said it DID make a difference (at least in benchmarks) for setups utilizing PCIe2.0.

I'm pretty sure it will all run great over native 8x/8x, was just curious if anybody could provide comparison in benchmarking numbers hence why I asked 🙂

[RockNRoll_Mulle]

Here is a Video showing different cards and SLI set up tested on Maximus V Extreme. 3-Way ASUS GTX660 Ti Performance Overview http://www.youtube.com/watch?v=UkNgL9VpyfY&list=PL13F5266778601CBA&index=8

[feniks]

thanks. watched it now, trying to get the numbers down for comparison. it seems however they tested the 2-way SLI only through the mixed (not officially supported slot configuration) 8x/16x, unless I missed when they said anything about testing them over 8x/8x configuration 😉

to sum things up, that's what has been tested:

AvP benchmark
1. primary slot testing (16x straight to CPU).

460
frames: 2500
avg frame time: 41.9ms
avg fps: 23.9

560Ti
frames: 3253
avg frame time: 32.2ms
avg fps: 31.1

660Ti
frames: 5284
avg frame time: 19.8ms
avg fps: 50.4

2. SLI (mixed 8x/16x slots via bridge chip)
2x 660Ti TOP
frames: 10166
avg frame time: 10.3ms
avg fps: 97.1

3. 3-way SLI (8x/16x/8x slots via bridge chip)
3x 660Ti TOP
frames: 14569
avg frame time: 7.2ms
avg fps: 139.1

I skipped Lucid MVP testing, because that usually doesn't work with a single card and latest nvidia driver (if it's newer than Lucid driver) AND AFAIK this feature doesn't work with SLI at all.

Still ... MVE board potentially allows 2-way SLI with 2 different slot configurations and assuming that review showed running not the suggested by manual 8x/8x (native) SLI configuration. hehe, good to see it works, but then there is no direct comparison to 8x/8x 2-way SLI configuration again LOL! 🙂

For now I am running native 8x/8x and things run smooth straight through the CPU. Maybe next time I drain the loop I will try 8x/16x configuration...

RockNRoll Mullet wrote:
Here is a Video showing different cards and SLI set up tested on Maximus V Extreme. 3-Way ASUS GTX660 Ti Performance Overview http://www.youtube.com/watch?v=UkNgL9VpyfY&list=PL13F5266778601CBA&index=8

[feniks]

just to update, all works fine through native 8x/8x, but I think about changing the configuration to 8x/16x whenever I drain the loop next time and compare my own benchmarks. wondering if there will be any gain (potentially secondary card could benefit from it).

[stackoverflow13]

I tried the 8x/16x it was horrible, but just didn't want to boot into sli mode. if you mage it I'd be interested to see how you fare.

[feniks]

really? dang ... not sure if I want to try it then ... 8x/8x feels great and I believe it's nowhere near the bandwidth saturation for 670 in SLI ... and with cards under water (solid link between them, short tubing around) ... it would be a major project to move them to "sandwich" slots.

might still try one day, now not so sure if that would be worth the hassle tho...

stackoverflow13 wrote:
I tried the 8x/16x it was horrible, but just didn't want to boot into sli mode. if you mage it I'd be interested to see how you fare.

[JorgeANeto]

I couldn't see any difference from using SLI (PCIe_X16/X8_1 + PCie_X8_2B - the black one) to SLI (PCIe_X16/X8_1 + PCie_x8_3) except by the lower VGA's temperatures in the second case (slots are more separated one from another). Was it suposed to exist a sensible diference?