Mother board for 4x GPU z170 build

[TinyMotel]

Hey y'all, title says it all.

Looking for a reliable z170 motherboard with a PLX chip so I can fit 4 gpus. SLI isn't a concern. I'll be using it for gpu based 3D rendering. Looking at using the 6700k as my CPU.

Pcpartpicker gave me only a few options:
Asus z170 WS
Gigabyte GA-Z170X-Gaming G1
EVGA z170 classified K
Gigabyte GA-Z170X-SOC FORCE

Would I be better off going for the 7700k / z270? Seems like 4x gpu setups are becoming more rare as they don't really scale well in gaming. However in 3D rendering the scaling is near 100%.

I'd even be open to ryzen, but I didn't see any 4x gpu boards.

Really just looking for the "cheapest" way to get 4gpus into a system.

Thanks!

 

[jaslion]

Hey y'all, title says it all.

Looking for a reliable z170 motherboard with a PLX chip so I can fit 4 gpus. SLI isn't a concern. I'll be using it for gpu based 3D rendering. Looking at using the 6700k as my CPU.

Pcpartpicker gave me only a few options:
Asus z170 WS
Gigabyte GA-Z170X-Gaming G1
EVGA z170 classified K
Gigabyte GA-Z170X-SOC FORCE

Would I be better off going for the 7700k / z270? Seems like 4x gpu setups are becoming more rare as they don't really scale well in gaming. However in 3D rendering the scaling is near 100%.

I'd even be open to ryzen, but I didn't see any 4x gpu boards.

Really just looking for the "cheapest" way to get 4gpus into a system.

Thanks!

There is a big problem atm. The 6700 and 7700 don't have enough pcie lanes to support 4 gpu's. They will work but have a lot slower transfer rate. Ryzen can support it better but doesn't have the motherboards yet and intels x99 is extremely expensive.

 

[TinyMotel]

Hey y'all, title says it all.

Looking for a reliable z170 motherboard with a PLX chip so I can fit 4 gpus. SLI isn't a concern. I'll be using it for gpu based 3D rendering. Looking at using the 6700k as my CPU.

Pcpartpicker gave me only a few options:
Asus z170 WS
Gigabyte GA-Z170X-Gaming G1
EVGA z170 classified K
Gigabyte GA-Z170X-SOC FORCE

Would I be better off going for the 7700k / z270? Seems like 4x gpu setups are becoming more rare as they don't really scale well in gaming. However in 3D rendering the scaling is near 100%.

I'd even be open to ryzen, but I didn't see any 4x gpu boards.

Really just looking for the "cheapest" way to get 4gpus into a system.

Thanks!

There is a big problem atm. The 6700 and 7700 don't have enough pcie lanes to support 4 gpu's. They will work but have a lot slower transfer rate. Ryzen can support it better but doesn't have the motherboards yet and intels x99 is extremely expensive.

 

[TinyMotel]

Thanks for chiming in!

Yeah, I thought a board with a PLX chip would help add lanes?

For example the asus z170 ws says it supports 4 way SLI. I'm assuming that's at 8x 4 way?

 

[jaslion]

Thanks for chiming in!

Yeah, I thought a board with a PLX chip would help add lanes?

For example the asus z170 ws says it supports 4 way SLI. I'm assuming that's at 8x 4 way?

It seems do be doing 8x 4 way. However the 6700k officially only supports up to 1 8x + 2* 4x. I'm not sure how this board makes it run 8x 4way.

 

[TinyMotel]

Yeah I'm not sure either. I guess the PLX chip does some blackmagic and allows the 4 8x GPUS.

Looks like on the Asus site, they're test machine was using a 6700k +4x Titan x.

That said, I can't find any info on there about what speed 4x GPUs runs at... or how many PCIE lanes the PLX chip adds.

 

[jaslion]

Yeah I'm not sure either. I guess the PLX chip does some blackmagic and allows the 4 8x GPUS.

Looks like on the Asus site, they're test machine was using a 6700k +4x Titan x.

That said, I can't find any info on there about what speed 4x GPUs runs at... or how many PCIE lanes the PLX chip adds.

That also makes me skeptical. Also which titan x do they use the first one or the second one? The PLX chip can't just magically add more lanes out of knowhere as z170 only has 20 lanes available.

 

[TinyMotel]

I just read the manual, and it's pretty vague on how it enables 4x GPU's but looks like it can run 2x GPU at x16 and 4x GPU at x8...

How? I have no idea... Is this just all a bad idea? Should I cough up the extra dough to go x99? hmmm

 

[TJ Hooker]

The PLX chip is a PCIe switch that adds extra lanes downstream of the switch. So you're right that there's only 16 lanes to the CPU, and that can be changed. So the GPU will think it has 8 lanes (which is required for SLI), and they actually will have 8 lanes worth of bandwidth between GPUs that are connected to the same PLX, but the bandwidth to the CPU is effectively only x4.

I have no idea how much bandwidth rendering requires. I know for gaming even a x4 connection usually suffers less than a 10% performance hit compared to x16, so you may be fine.

 

[jaslion]

The PLX chip is a PCIe switch that adds extra lanes downstream of the switch. So you're right that there's only 16 lanes to the CPU, and that can be changed. So the GPU will think it has 8 lanes (which is required for SLI), and they actually will have 8 lanes worth of bandwidth between GPUs that are connected to the same PLX, but the bandwidth to the CPU is effectively only x4.

I have no idea how much bandwidth rendering requires. I know for gaming even a x4 connection usually suffers less than a 10% performance hit compared to x16, so you may be fine.

Ryzen has 24 lanes so thats also not really an option. The only way I can see this working is by going x99.

 

[TJ Hooker]

The PLX chip is a PCIe switch that adds extra lanes downstream of the switch. So you're right that there's only 16 lanes to the CPU, and that can be changed. So the GPU will think it has 8 lanes (which is required for SLI), and they actually will have 8 lanes worth of bandwidth between GPUs that are connected to the same PLX, but the bandwidth to the CPU is effectively only x4.

I have no idea how much bandwidth rendering requires. I know for gaming even a x4 connection usually suffers less than a 10% performance hit compared to x16, so you may be fine.

Ryzen has 24 lanes so thats also not really an option. The only way I can see this working is by going x99.

I don't understand where you're coming from here. Like I said, even with only 16 PCIe lanes from the CPU, a PLX switch allows up to 4 GPUs to have x8 bandwidth between each other and x4 bandwidth to the CPU, which may be sufficient bandwidth for rendering (is pretty much sufficient bandwidth for gaming anyway).

Also, Ryzen may have 24 lanes on paper, but 4 lanes are used for the connection to the chipset, and 4 more are typically used for an M.2 slot. So in practice you'll only have 16, maybe 20, CPU PCIe lanes with Ryzen.

 

[TinyMotel]

Awesome. Thanks guys for chiming in here.

4x is probably fine. Really the only time the bandwidth is considered in 3D rendering is when you initially send a scene to the GPUs so I guess I could see a little lag there.

Really as long as I can slot 4 gpus in and it posts and is stable I'm happy. Looking to make a budget build, with top of the line gpus. Probably 4 1080tis. But this will just be a render node tied to my main workstation + a few other dual xeon machines...

Seems like Asus z170ws is the board to get or are there others I should consider??