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eGPUs still bottlenecked by thunderbolt?

staykoff
By staykoff
in Graphics Cards
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Hey guys,
I've been interested in buying an eGPU soultion for a while now but last I checked 1-2 years ago eGPUs were severely bottlenecked by thunderbolt bandwidth capacity and were effectively functioning at 60% of max potential and one had to crack open their notebook and connect the GPU to the internal PCMCIA slot if they wanted to obtain the full bandwidth. I am just curious if anything has changed now with thunderbold 3 etc?  Does eGPU make more sense now? Thanks.

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3 minutes ago, staykoff said:

Hey guys,
I've been interested in buying an eGPU soultion for a while now but last I checked 1-2 years ago eGPUs were severely bottlenecked by thunderbolt bandwidth capacity and were effectively functioning at 60% of max potential and one had to crack open their notebook and connect the GPU to the internal PCMCIA slot if they wanted to obtain the full bandwidth. I am just curious if anything has changed now with thunderbold 3 etc?  Does eGPU make more sense now? Thanks.

AFAIK it's only ever been really possible with TB3, and since GPUs have gotten faster in the meantime, the problem is actually probably worse now. TB4 doesn't increase bandwidth, so don't expect this problem to get better soon.

 

The internal slots are generally x1, so they actually work worse than TB3. It's primarily for hacking a GPU into a machine without TB.

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Yes, and you will never not be bottlenecked.  (I Still fucking hate that term)

 

A Video card is intended to run at PCI-E Gen 3 or 4 x16 speeds.  (x8 at a minimum)

 

At no point will you get an external interface that is that fast.  Period.  

 

(Also:  It was probably the NVME Slot, not PCMCIA, which is still only x4 speeds.)

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Is it true that the bottleneck only applies to when trying to use the internal laptop monitor and goes away if an external monitor is used?

 

52 minutes ago, tkitch said:

It was probably the NVME Slot, not PCMCIA, which is still only x4 speeds.

Sorry I got that wrong. It was mPCIe or NGFF/M.2.

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3 hours ago, staykoff said:

Is it true that the bottleneck only applies to when trying to use the internal laptop monitor and goes away if an external monitor is used?

 

Sorry I got that wrong. It was mPCIe or NGFF/M.2.

Either using the internal screen or an external connected screen to the egpu it will still be a bottleneck. It is less of a bottleneck when using a screen directly connected to the egpu as it doesn't send the data for the screen back through the wire.

There are also different thunderbolt 3 configurations with either 2 or 4 lanes. 4 is a requirement in my opinion or the bottleneck is too high. 

With my 1080 egpu and my dell laptop with 4 lane tb I am able to get about 85% of the performance vs when I put it directly in a tower. The higher power gpu you put in the worse the bottleneck would get as it sends more data. 

Like if you put a 3090 in a egpu enclosure, that might be bottlenecked up to like 50%.

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12 minutes ago, m9x3mos said:

Either using the internal screen or an external connected screen to the egpu it will still be a bottleneck. It is less of a bottleneck when using a screen directly connected to the egpu as it doesn't send the data for the screen back through the wire.

There are also different thunderbolt 3 configurations with either 2 or 4 lanes. 4 is a requirement in my opinion or the bottleneck is too high. 

With my 1080 egpu and my dell laptop with 4 lane tb I am able to get about 85% of the performance vs when I put it directly in a tower. The higher power gpu you put in the worse the bottleneck would get as it sends more data. 

Like if you put a 3090 in a egpu enclosure, that might be bottlenecked up to like 50%.

Hypothetically speaking, if one could connect the card directly to the PCIe slot in the motherboard of the laptop with some sort of extension cable, wouldn't that offer maximum performance?

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It would in theory if it existed. Laptops don't have pcie slots similar to desktops to plug into though. 

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17 hours ago, m9x3mos said:

It would in theory if it existed. Laptops don't have pcie slots similar to desktops to plug into though. 

Considering that Razer has a notebook and also an eGPU solution wouldn't it make sense for them to add a PCIe port to their notebook?

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3 hours ago, staykoff said:

Considering that Razer has a notebook and also an eGPU solution wouldn't it make sense for them to add a PCIe port to their notebook?

Except they didn't. The last one from them I saw was also just using tb3. 

If they wanted to add a different connector they would need to come up with their own connector. Pretty sure dell did this. And the cpu they are using would also be able to have enough lanes to support it. 

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  • 2 months later...
Posted

You will still be bottlenecked, unless you use a TB3. to PCI-E x4 with 40 Gbps bandwidth and a GPU that only has x4 PCI-E lanes ( like the gt 1030 ).

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