make 2 thunderbolt work in parallel?
 
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make 2 thunderbolt work in parallel?  

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(@gu_tally)
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Joined: 3 years ago
 

just a thought

if there is some sort of board that have a plx chip that can reverse birificate the two x4 into a x8, the egpu bottleneck will be significantly reduced.

2021 17" Dell Precision 7760 (RTXA4000) [11th,8C,H] + RX 6800 XT @ 64Gbps-M.2 (ADT-Link R43SG 4.0) + Win11 [build link]  

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(@bastien_loiseau)
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Joined: 8 months ago
 

@gu_tally, I was wondering the same.

On my MBP there is 2 x TH2 ports, and on my eGPU there is also 2 ports (TH3 but with the right adapters...)

Could, pluging two TH2 cable from the MBP ports to the two TH3 ports on the BM eGPU, speed up by 2X the performances?

 

-Late 2014 Mac BookPro 15", Patched on Moterey.
-Blackmagic eGPU, Radeon Pro 580 with 8 GB GDDR5


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Boltoway
(@boltoway)
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Joined: 3 years ago

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(@bastien_loiseau)
Active Member
Joined: 8 months ago
 

@boltoway, It was too good to be true...

 

-Late 2014 Mac BookPro 15", Patched on Moterey.
-Blackmagic eGPU, Radeon Pro 580 with 8 GB GDDR5


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surfacedockguy
(@surfacedockguy)
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Joined: 2 months ago
 

@boltaway @bastien_loiseau/

 

Even if you could aggregate two Thunderbolt ports on a laptop, the bandwidth to the CPU is ultimately limited to Gen3x4 anyway so the two ports would still share bandwidth.

On future Gen4/Gen5 platforms, its more plausible because a dual-port Thunderbolt host controller could be fed by Gen4x4, then bifurcate to 2x Gen3x4. One of the Apple M2 systems might already do this.

 

There is precedent for PCI lane aggregation in data centers: https://patents.google.com/patent/US9846669B2/en But that has a whole different set of problems than our simple eGPU case Smile

 

 

 

RX 570 | TH3P4mini dock | Surface Laptop Studio
(Code 12 in Win11 just like EG200)


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joevt
(@joevt)
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Joined: 5 years ago
 
Posted by: @surfacedockguy

Even if you could aggregate two Thunderbolt ports on a laptop, the bandwidth to the CPU is ultimately limited to Gen3x4 anyway so the two ports would still share bandwidth.

On future Gen4/Gen5 platforms, its more plausible because a dual-port Thunderbolt host controller could be fed by Gen4x4, then bifurcate to 2x Gen3x4. One of the Apple M2 systems might already do this.

Current platforms with integrated Thunderbolt controllers (Ice Lake, Tiger Lake, M1, M2) are not limited by a PCIe Gen 3 x4 connection between the Thunderbolt host controller and the host CPU. @itsage did bandwidth tests on Ice Lake where two ports of the same Thunderbolt bus were able to do 4668 MB/s total which would require at least PCIe 3 x8 connection.
  https://egpu.io/forums/laptop-computing/ice-lake-cpu-on-die-thunderbolt-3-controller-bandwidth/

Intel Thunderbolt controllers (integrated or discrete) have two ports per Thunderbolt bus where each Thunderbolt bus has up to two DisplayPort connections. 

For M1 and M2, each Thunderbolt port belongs to a separate Thunderbolt bus with two DisplayPort connections.

In any case, there's no way to use multiple Thunderbolt connections for a single PCIe device. @itsage's test used multiple Thunderbolt connections to multiple PCIe devices (one connection per NVMe) and combined them using RAID 0. For GPUs, such a setup would be something like SLI or CrossFireX which usually requires motherboard support and is therefore probably not doable with Thunderbolt connections.
  https://www.makeuseof.com/reasons-multi-gpu-gaming-setups-are-done/

 

Mac mini (2018), Mac Pro (Early 2008), GA-Z170X-Gaming 7, Sapphire Pulse Radeon RX 580 8GB GDDR5, Radeon Pro W5700, Sonnet Echo Express III-D, Trebleet Thunderbolt 3 to NVMe M.2 case


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