SLI/CF w/ external TB-GPUs?

[yaya1]

Last night, I had this idea: Quite a few more expensive notebooks have two or more usb type-c ports, often multiple of them are thunderbolt-powered meaning -in theory- you could attach multiple graphics cards to those notebooks using enclosures. I'd definitely be curious about the performance and/or scaling...

So, did anyone ever try this? Seeing it in a future video would be awesome...

(Sorry for my bad english, I'm german...)

[Droidbot]

this is a good idea but it REALLY depends on the machine you do it on

 

something like an xps 15 would have problems as the TB3 ports are wired through the PCH, so you have 2x pci-e x4 going through a pci-e x4 bus to the processor. 

but on the macbook pro 15, the TB3 ports are wired to the CPU, so up to all 4 ports at once would be fucking insane hahah

[SoreRaito]

 

[yaya1]

@DroidbotYeah, I already thought about this, too. 

[yaya1]

6 minutes ago, SoreRaito said:

 

I know quite a big chunk of performance will be lost anyways...

[Mira Yurizaki]

There's some unknowns here I think. Even if you have two Thunderbolt ports, do they have their own 40Gbps link or do they share it?

[yaya1]

That depends on how they are wired...

[Droidbot]

2 minutes ago, M.Yurizaki said:

There's some unknowns here I think. Even if you have two Thunderbolt ports, do they have their own 40Gbps link or do they share it?

PCH Wired: each port has 40Gbps (unless explicitly wired as x2, like the XPS line) BUT gets fed through the PCH, which is 40Gbps. 

CPU Wired: each port has 40Gbps, and uses 4 of the 16 lanes that the CPU provides. 

[yaya1]

4 minutes ago, M.Yurizaki said:

There's some unknowns here I think. Even if you have two Thunderbolt ports, do they have their own 40Gbps link or do they share it?

Look: 

 

[DrMacintosh]

Most laptops do not support Thunderbolt to the fullest, however the MacBook Pros do, so if this ever was possible a Mac would probably be the way to do it. Although it would probably have to be Crossfire, not SLI because Nvidia makes you use a bridge 

[yaya1]

@DrMacintoshCrossfire uses the Motherboard to link the gpus though. How is that going to end up? 

[DrMacintosh]

Just now, Jonas_2909 said:

How is that going to end up? 

Same way that it does normally. 

[yaya1]

@RandomGuy13The question is though: Will a macbook's chip be capable of doing that? If one were to use a macbook...

[DrMacintosh]

Just now, Jonas_2909 said:

Do you think it would work anyways? 

SLI has more variables. SLI would have to link two GPUs that are hooked up two separate ports in two separate enclosures with a long SLI bridge......Crossfire could do the same thing but all through Thunderbolt. 

[yaya1]

@DrMacintoshYou're right. 

[DrMacintosh]

4 minutes ago, Jonas_2909 said:

@RandomGuy13The question is though: Will a macbook's chip be capable of doing that? If one were to use a macbook...

It's probably the best bet for this theoretical situation. 

[Mira Yurizaki]

13 minutes ago, RandomGuy13 said:

They most likely share it, and if not then they are on their own USB busses giving it one more reason not to work, But 40Gbps is equivalent to a Gen 3 4x PCIe connection, correct me if I am mistaken. And SLI requires at least a 8x which means SLI is not possible. However Cross fire only needs 4x, however 40Gbps is only 4x and since you need two 4x, even that may not be possible.

 

EDIT: SLI requires at least Gen 2.0 8x which is technically equivalent to a Gen 3 4x but SLI does not support gen3 4x for whatever reason.

You can probably get away with a PCI Express switch.

 

Probably.

[System Error Message]

you can SLI over thunderbolt but its going to be tricky or funny. Just grab yourself the bridge and connect the cards together.

It will work if over PCIe but you will not get a performance benefit because of additional thunderbolt overheads and only 4 lanes.

[Jazzsus]

On 07.08.2017 at 6:29 PM, M.Yurizaki said:

You can probably get away with a PCI Express switch.

 

Probably.

Isn’t it 4x for each Thunderbolt 3 port?

[yaya1]

On 03/04/2018 at 9:59 AM, Jazzsus said:

Isn’t it 4x for each Thunderbolt 3 port?

I think yes, it is. At least on most laptops...It should still scale, though, should it? I mean you'd still be using two GPUs...

Edited April 5, 2018 by Jonas_2909
Typo

[Jazzsus]

8 hours ago, Jonas_2909 said:

I think yes, it is. At least on most laptops...I should still scale, though, should it? I mean you'd still be using two GPUs...

You are 100% going to get the same fantastic bang for your buck you do with crossfire (not good). It also really depends on the laptop you use and the enclousure. Things like the Sonnet Echo Express iii-r https://www.amazon.com/Sonnet-Express-Thunderbolt-Rackmount-Expansion/dp/B00G7LQJC4 can take 2 (maybe 3) gpus in one enclousure and run them in crossfire. This was tested as far I know of on the MacBook Pro but that is the only one I found. There is also masaive overhead because you are running 2 egpus of one tb3 cable. Though I also have heard of people doing crossfire and sli on two diferent enclosures (i can’t confirm that) but it was preatty hard for anyone with technical know how. If you are going to try the second option check the tb 3 controller speed also (40gbs Per port).

[Droidbot]

30 minutes ago, Jazzsus said:

You are 100% going to get the same fantastic bang for your buck you do with crossfire (not good). It also really depends on the laptop you use and the enclousure. Things like the Sonnet Echo Express iii-r https://www.amazon.com/Sonnet-Express-Thunderbolt-Rackmount-Expansion/dp/B00G7LQJC4 can take 2 (maybe 3) gpus in one enclousure and run them in crossfire. This was tested as far I know of on the MacBook Pro but that is the only one I found. There is also masaive overhead because you are running 2 egpus of one tb3 cable. Though I also have heard of people doing crossfire and sli on two diferent enclosures (i can’t confirm that) but it was preatty hard for anyone with technical know how. If you are going to try the second option check the tb 3 controller speed also (40gbs Per port).

Echo 3 offers that at a high price. 

 

As long as both TB3 ports are on the same bus you will be alright, still not recommended though. 

[Jazzsus]

13 hours ago, Droidbot said:

Echo 3 offers that at a high price. 

 

As long as both TB3 ports are on the same bus you will be alright, still not recommended though. 

Neither did I. I just said it works.