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AMD Navi & PCIe 4.0 eGPU?  

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Phoenix2063
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Thought I'd start a thread ahead of the June 10th unveiling of AMD Navi at E3 which also includes PCIe 4.0 compatibility. From the computex demo we should be looking at RTX 2070 performance and perhaps 10% faster in AMD tailored games. Although that was using a PCIe 4.0 motherboard which I'm unsure if eGPU's would even integrate at all?

Navi likely to launch alongside their new Ryzen chips on 7th July. 

In addition to this summer's Navi launch, AMD's roadmap has 'Navi plus' arriving early next year which going by the computex demo targeting the RTC 2070, will likely be their higher end models going after the 2080 and maybe even the 2080ti.

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Defoler
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Lets be honest.
Even PCI 3.0 currently in an eGPU system, isn't being fully utilized.
Our current problem is not PCIE but TB3 bandwidth.
USB 4, which will replace TB3, is set to be 40Gb/s, just like TB3. So bandwidth wise, it isn't going to allow us to even utilize PCIE 4.0. And since PCIE 4.0 will be backward compatible, we should be able to put PCIE 4.0 cards in the current PCIE 3.0 envelopes.
Whether we will get new envelopes with PCIE 4.0, will even depends if we need them. PCIE 4.0 vs PCIE 3.0 should give you the exact same results, as you are only limited to the connector.

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OliverB
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@defoler
(you are not @defiler, right? We had this confusion already)
40 GBs is supposed to be enough if the application/game is well programmed. I don't see any point in USB 4, moreover it's the same bandwidth?! What exactly is the gain?

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Defiler
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Posted by: OliverB

@defoler
(you are not @defiler, right? We had this confusion already)
40 GBs is supposed to be enough if the application/game is well programmed. I don't see any point in USB 4, moreover it's the same bandwidth?! What exactly is the gain?

No he's not, but I keep getting notifications I'm being mentioned in posts. Smile

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Defoler
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Posted by: OliverB

@defoler
(you are not @defiler, right? We had this confusion already)
40 GBs is supposed to be enough if the application/game is well programmed. I don't see any point in USB 4, moreover it's the same bandwidth?! What exactly is the gain?

No, not the same person Smile It was asked several times by now.

And look at the USB 4.0 proposed specs.

USB 4.0 is basically an update to USB 3.2 with TB3 becoming free entered into the mix. To make both TB3 and USB 3.2 becoming a more coherent standard. After all, 3.0, 3.1, 3.2, is way too confusing to 99% of people. So moving to USB 4.0 is just making sense of the standards.

USB 3.2 is limited to 20Gb/s (driven from TB3), and so USB 4.0 is going to be an upgraded version of that, allowing 40Gb/s with certified cables (just like you need today for TB3 to gain 40Gb/s). Also note the small b.

Anyway, PCIE 3.0 is limited to 15.7GB/s at full x16 lanes,  and PCIE 4.0 is going to give double that.
But note the B, not b. Meaning PCIE 3.0 is basically 125.6Gb/s (or TB3 is just 5GB/s), which is already 3 times that of TB3. So PCIE 4.0 will be 6 times faster than USB 4.0 or TB3.
Trying to stick PCIE 3.0 full data transfer ability to TB3/USB 4.0 will be like trying to cram an elephant into 2x2m shop. Trying to do that with PCIE 4.0 will be trying to cram a t-rex into the same space, and expect not to be eaten in the process.

You understand now the difference and why USB4, PCIE3.0, PCIE4.0, aren't going to matter for us?
We are already at the peak of data transfer to the external PCIE connection. Even if you have the best software running full 40Gb/s, you are not even tickling PCIE 3.0, let alone PCIE 4.0 (or even PCIE 5.0 expected to already come not so far away).

And even in reverse, PCIE 4.0 is bringing their own special PCIE connector, OCuLink-2, a standard which is an alternative to TB3, and it runs at 8GB/s (or 64Gb/s, 1.6x of TB3/USB 4.0). And even that isn't going to be even nearly enough to saturate PCIE 3.0, let alone PCIE 4.0 which rely on it.

So TL;DR:
No, PCIE 4.0 and USB 4.0 are going to do jack shit to us. 2080 TI will still be bottlenecked using eGPU. Even radeon VII and 2080 are on that verge.
And the new cards will be just as bottlenecked, meaning we are already reaching the max we are going to get. If you get a 2x faster card than 2080TI, it will not be enough to run it through PCIE 4.0 x4 to gain its full performance. Most likely you will hinder it by 30% at least. The faster the card, the more you lose bottlenecking it.

Until we get faster connector (at least 2x of TB3/USB 4.0), we will only see dGPU inside the laptops becoming faster than any eGPU setup you can use in a few years.
Even OCuLink-2 isn't going to cut it. 
And lets be honest, I don't see apple making a special OCuLink-2 connector to their laptops (maybe only a couple laptop makers at most on special laptops), so apple at least, will be limited and so will most other laptop makers.

This post was modified 1 year ago
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Phoenix2063
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Third party Navi prototypes on show at computex, ditched the blower style card
https://www.google.com/amp/s/amp.tomshardware.com/news/navi-prototype-cards,39528.html

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Phoenix2063
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Here we are talking about PCIe 4.0 when PCIe 5.0 has been announced at 128gbs transfer speeds so double PCIe 4.0! 😯 
https://www.google.com/amp/s/www.techspot.com/amp/news/80310-pcie-50-specification-announced-offer-128gbs-transfer-speeds.html

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Eightarmedpet
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Posted by: Phoenix2063

Third party Navi prototypes on show at computex, ditched the blower style card
https://www.google.com/amp/s/amp.tomshardware.com/news/navi-prototype-cards,39528.html

I really hope there are less garish options.

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joevt
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Posted by: Defoler
Posted by: OliverB

40 GBs is supposed to be enough if the application/game is well programmed. I don't see any point in USB 4, moreover it's the same bandwidth?! What exactly is the gain?

look at the USB 4.0 proposed specs.

USB 4.0 is basically an update to USB 3.2 with TB3 becoming free entered into the mix. To make both TB3 and USB 3.2 becoming a more coherent standard. After all, 3.0, 3.1, 3.2, is way too confusing to 99% of people. So moving to USB 4.0 is just making sense of the standards.

It's called USB4. They removed the space and decimal point. Yeah, the only gain I see is they added TB3. The USB spec is open (freely available), so maybe it will make TB3 spec open as well (or maybe they'll continue to hide it like they currently do, and like VESA DisplayPort 1.4 spec etc.).

Posted by: Defoler

USB 3.2 is limited to 20Gb/s (driven from TB3)

USB 3.2 is limited to 10 Gb/s x2 (two lanes, 20 Gb/s total) (driven from USB 3.1). It also adds 5 Gb/s x2 (two lanes, 10 Gb/s total) (driven from USB 3.0). Thunderbolt is actually 10.3125 Gb/s x2 (two lanes, 20.625 Gb/s total) or 20.625 Gb/s x2 (two lanes, 41.25 Gb/s total). They are all two lane, full-duplex protocols (separate lanes for send and receive, four lanes total). All full-duplex two lane protocols require a USB-C connector at both ends because USB-A can only do one full-duplex one lane protocol (USB 3.2 gen 2 x1 max).

USB-C has a DisplayPort alt mode that uses four lanes in one direction (the receive lanes are used as transmit lanes) (USB 2.0 is still available as separate data lines). Another DisplayPort alt mode combines two lanes of DisplayPort and one lane of USB 3.1. Virtual Link is another USB-C alt mode similar to DisplayPort alt mode, except the two USB 2.0 data lines can support USB 3.1 gen 2 (requires special cable).

The alt modes are separate from the USB spec. Thunderbolt is also an alt mode. But with USB4, it is not an alt mode anymore? Instead, I guess it becomes the main mode and works as Thunderbolt always did (includes PCIe and DisplayPort packets and allows for custom packets such as Thunderbolt network IP, Thunderbolt Target Display Mode, and Thunderbolt Target Disk Mode (the last two are currently MacOS only and the protocol is unknown so you can't create a driver for Windows or Linux). USB4 traffic for USB4 devices can be a new packet type. Older Thunderbolt devices can ignore packets that they don't understand - the packets are not addressed to them. This is similar to network packets that you would see from an Ethernet port, except this is a USB4 port.

Posted by: Defoler

and so USB 4.0 is going to be an upgraded version of that, allowing 40Gb/s with certified cables (just like you need today for TB3 to gain 40Gb/s).

USB4 combines USB 3.2 and Thunderbolt. I haven't read anything about what's been added on top of those.

Posted by: Defoler

Anyway, PCIE 3.0 is limited to 15.7GB/s at full x16 lanes,  and PCIE 4.0 is going to give double that.
But note the B, not b. Meaning PCIE 3.0 is basically 125.6Gb/s (or TB3 is just 5GB/s), which is already 3 times that of TB3. So PCIE 4.0 will be 6 times faster than USB 4.0 or TB3.

PCIe 3.0 is 126.03 Gb/s (after accounting for the 128b/130b encoding).
Thunderbolt 3 is 40 Gb/s (after accounting for the 64b/66b encoding). Same for USB4, I guess.
USB 3.2x2 is 19.39 Gb/s (after accounting for the 128b/132b encoding).

But the difference between Thunderbolt and PCIe is worse than what you stated because PCIe traffic over Thunderbolt is limited to 22 Gb/s so PCIe 3.0 x16 is 5.73 times greater and PCIe 4.0 x16 is 11.46 times greater. Even PCIe 1.0 x16 is faster than Thunderbolt. Maybe USB4 will allow the entire Thunderbolt bandwidth to be used for PCIe traffic when no other type of traffic exists instead of just 22 Gb/s? That would be nice but it won't affect existing Thunderbolt devices (unless 40 Gb/s was always an option and only a firmware update is required to unlock it).

Posted by: Defoler

Trying to stick PCIE 3.0 full data transfer ability to TB3/USB 4.0 will be like trying to cram an elephant into 2x2m shop. Trying to do that with PCIE 4.0 will be trying to cram a t-rex into the same space, and expect not to be eaten in the process.

You understand now the difference and why USB4, PCIE3.0, PCIE4.0, aren't going to matter for us?
We are already at the peak of data transfer to the external PCIE connection. Even if you have the best software running full 40Gb/s, you are not even tickling PCIE 3.0, let alone PCIE 4.0 (or even PCIE 5.0 expected to already come not so far away).

And even in reverse, PCIE 4.0 is bringing their own special PCIE connector, OCuLink-2, a standard which is an alternative to TB3, and it runs at 8GB/s (or 64Gb/s, 1.6x of TB3/USB 4.0). And even that isn't going to be even nearly enough to saturate PCIE 3.0, let alone PCIE 4.0 which rely on it.

OCuLink-2 is 63.02 Gb/s (7.88 GB/s), 2.86 times more than 22 Gb/s Thunderbolt or 1.58 times more than 40 Gb/s Thunderbolt (if it ever exists).

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OliverB
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@defiler and @defoler
you guys really rule! you are the reason why this community lives with humor and good information.
Thank you very much, Sirs.

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