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ASUS Maxim VIII Hero - Help - PCIe Bus lanes 2x16(8x8 Dual) and 1x4 PCIe

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BLAs68

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Aug 11, 2016
Hello, I always get confused over how bus lanes work so I want ask the community here about a specific configuration of GPUs on the motherboard regarding one dedicated PhysX card in addition to the normal use GPU. What is the best placement on the bus lanes?

I'd like to put the dedicate PhysX card on the x4 lane so it does not have the x16 lanes going into dual x8 mode. The two cards not being so close and hot is a nice added factor but I'm not sure what would occur if I had it in the 4x lane.

I'm wondering that it would definitely go into x8 dual mode if I had both the PhysX and normal card in the x16 lanes.

I understand that there's much talk over the little improvement over having them in dual but would the x4 slot being used affect the x16 lanes or is it more of a standalone bus lane?

Thanks!
 
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BLAs68

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Aug 11, 2016
I'm sorry I'm not on my PC right now so I'll give a basic run down

i7 6700k
Essence STX II 7.1 Sound Card
Pascal Titan X
Original Titan 6GB As dedicated PhysX card

Samsung 250 GB SSD for Windows, core and important files
Samsung 540 GB (I believe) for secondary files
2x 4TB HGST HDDs for backup files

Arctic Freezer Pro Rev 2 CPU Cooling

G.SKILL Ripjaws V Series 16GB (2 x 8GB) DDR4 SDRAM2400

EVGA SuperNOVA 1300 G2, 80+ GOLD 1300W

Thermaltake Chaser Series Chaser MK-I Black SECC ATX Full Tower Computer Case
 
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ATMINSIDE

Sim Racing Aficionado Co-Owner
Joined
Jun 28, 2012
With a Pascal Titan X it's a waste of power and cooling to put a GPU in for PhysX. Go sell the old Titan, you'll get a lot more from it that way.
 
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BLAs68

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Aug 11, 2016
Thanks but I've been hesitant to that idea because I bought a second Titan last year and hoped to sell the recent one and save my original. But most likely on the x4 lane the Titan would hinder the pascal's performance?

Really like that Titan though so I'm going to keep it in use possibly until the day I test the performance with and without PhysX, hopefully there would be at least a subtle difference even with the Pascal. I don't mind the extra power use though, since I can still salvage parts that do well even with age.

I don't want to deviate from the topic since it's a motherboard thread, so rolling back, how would the system configure itself if a PhysX card was put in the secondary x16 lane? If it was put in a x4 lane?
 

ATMINSIDE

Sim Racing Aficionado Co-Owner
Joined
Jun 28, 2012
It's highly likely you'll hinder performance because of the heat unless you have fantastic airflow in your case. Not just on x4, but by having the extra card there period.
 
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BLAs68

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Aug 11, 2016
Ahh thanks I think I see what you mean, having to process another card would impact it, no? Otherwise I have great airflow.
 

Woomack

Benching Team Leader
Joined
Jan 2, 2005
Most games are not even using physx anymore and even if they do then you will barely see performance difference when you add dedicated card for physx. It's only additional wattage/heat ( and noise if you run it on air ).
Regardless if you use dedicated card in PCIe x4 or x16, performance won't change just because even x4 has high enough bandwidth for physx data. There were even motherboards with description that x4 slot is dedicated for physx card ( could be used for anything but it was gaming series so they had to show it's somehow special ;) ).
 
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BLAs68

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Aug 11, 2016
Thanks for clarifying those subjects. My plan ended in failure because the motherboard front panel connectors were blocking the GPU from being inserted in the last slot. Even with a riser/extension cable the GPU was not being detected in the 4x slot. No idea if it's motherboard specific or that the PhysX GPU, in order to be enabled or detected, would have to parallel the main GPU in a position that it could sli; which would not be possible in the x4 slot.

I was wondering if the mobos for Skylake even supported dual x16 lanes. Hours and money on that riser wasted.
 

EarthDog

Gulper Nozzle Co-Owner
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Dec 15, 2008
Location
Buckeyes!
Physx cards can be in a 4x slot. It is SLI that does not work below 8x.

Scrap the second card bud. :)
 
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BLAs68

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Aug 11, 2016
It pains me to trade off my og Titan but I think now's the time with all the Nvidia hype. But still why wasn't the GPU being detected in the Maximus VIII Hero? The PCIEX_4 slot I used shared bandwidth with 1_2 and 1_3, and would disable them if used. There was also a tip in the Bios graphics section that shows that if a second GPU would be added, it should be inserted into the x8_2 lane so the dual GPUS could run in x8. No mention at all that a GPU could be inserted into the x4 lane and be detected, even though it really should. That's just grinding my gears.
 

EarthDog

Gulper Nozzle Co-Owner
Joined
Dec 15, 2008
Location
Buckeyes!
Ribbon cable may be bad... you can test that by plugging in the gpu to that slot (yes, you will have to take out your front panel thing getting in the way).
 

ATMINSIDE

Sim Racing Aficionado Co-Owner
Joined
Jun 28, 2012
It pains me to trade off my og Titan but I think now's the time with all the Nvidia hype. But still why wasn't the GPU being detected in the Maximus VIII Hero? The PCIEX_4 slot I used shared bandwidth with 1_2 and 1_3, and would disable them if used. There was also a tip in the Bios graphics section that shows that if a second GPU would be added, it should be inserted into the x8_2 lane so the dual GPUS could run in x8. No mention at all that a GPU could be inserted into the x4 lane and be detected, even though it really should. That's just grinding my gears.

Because the motherboard manufacturers assume you're going to be using SLI, not a completely unnecessary addition of a GPU for PhysX.
 
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BLAs68

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Aug 11, 2016
It's not the ribbon, I think, I tested it out in the slots. Works fine, although maybe an extension is too much for a x4 slot. I was about to bend those panel connectors that time, cut em and solder them, buy a new mobo. Is there any other reason that could be causing the GPU being undetected?
 
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BLAs68

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Aug 11, 2016
Because the motherboard manufacturers assume you're going to be using SLI, not a completely unnecessary addition of a GPU for PhysX.

So likely they configured the lanes in way that a non primary GPU in the X4 slot wouldn't be detected?
 

ATMINSIDE

Sim Racing Aficionado Co-Owner
Joined
Jun 28, 2012
So likely they configured the lanes in way that a non primary GPU in the X4 slot wouldn't be detected?

No, I'm saying they wouldn't tell you about your statement "No mention at all that a GPU could be inserted into the x4 lane and be detected, even though it really should." because so few people use a dedicated PhysX card these days.
 
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BLAs68

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Aug 11, 2016
There was no way I could get my Pascal X running at x16 with a PhysX card at x4.

I'm wondering about a good PhysX game that I could reference to and test with the Og Titan sitting at the corner as a PhysX and the new Pascal X as the lead. Going to pop it into x8 dual sli mode and compare the performances.