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Defoler
(@defoler)
Eminent Member
Joined: 2 years ago
 

@joevt
A few things.

It's called USB4

Even if its called USB4, I have a feeling we will get USB 4.1 and 4.2 at some point. They never make up their mind.

USB4 combines USB 3.2 and Thunderbolt.

That is what I said. They even said so on the drafts and the end spec.

It also adds 5 Gb/s x2 (two lanes, 10 Gb/s total) (driven from USB 3.0).

That is not correct. USB 3.0 does not have 5Gb/s x2. It is still based and locked in terms of standard to the old A  connector, which was only able to allow 5Gb/s on a single data lane.
USB 3.1 was also locked to A connector (locked I mean that they were forced to also allow those speeds on the A connector), and because of that, 3.1 allowed only 10Gb/s with the compression, and only that through gen 2. Gen 1 was also locked to 5Gb/s just like 3.0.

USB 3.2 allows two lanes through USB-C and compression, but the use of two lanes, is thanks to TB3. TB3 standard came out in 2016 from apple and intel, and the usb-c standard which came after was allowed through support from intel. So USB 3.2 was not driven by USB 3.1 but more by TB3 from intel and apple, who wanted USB-C hardware to be more common for apple.

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

What you are saying is that correct.
TB3 has 40Gb/s if you also account for the usb-c data reserves. It does indeed has 22Gb if you split and allow USB to transfer through it (which some of the cases do). But the standard allow non split data transfer, which allows full 40Gb/s connection.
That is part of the difference for example between the razer chroma core and the X. The X has a 40Gb/s hardware (I have seen a couple of youtubers actually testing it). It does not split and uses the full data lanes. So you are more limited by the data cables. The chroma has a split to data and usb in order to drive the ethernet and 4xusb connectors seperately from the PCIE data stream

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joevt
(@joevt)
Noble Member
Joined: 3 years ago
 
Posted by: Defoler

Even if its called USB4, I have a feeling we will get USB 4.1 and 4.2 at some point. They never make up their mind.

I'm guessing they made up their mind to stop using point releases, so the next version will be USB5 but we'll have to wait and see since I can't find clear confirmation about the reasoning behind the new name (other than to simplify it).

Posted by: Defoler

USB4 combines USB 3.2 and Thunderbolt.

That is what I said. They even said so on the drafts and the end spec.

You said it was an upgrade of 3.2 as if 3.2 was getting new features. I called it a combination of 3.2 and Thunderbolt because the new features are from Thunderbolt and don't affect the 3.2 part.

Posted by: Defoler

It also adds 5 Gb/s x2 (two lanes, 10 Gb/s total) (driven from USB 3.0).

That is not correct. USB 3.0 does not have 5Gb/s x2.

I meant that the 5 Gb/s speed is from USB 3.0. Using dual lane (x2) is new to USB 3.2. I am confused by what you mean when you said "driven from TB3". Maybe you mean that the higher speed (dual lane) modes of USB 3.2 were created to compete with TB3?

Posted by: Defiler

It is still based and locked in terms of standard to the old A  connector, which was only able to allow 5Gb/s on a single data lane.
USB 3.1 was also locked to A connector (locked I mean that they were forced to also allow those speeds on the A connector), and because of that, 3.1 allowed only 10Gb/s with the compression, and only that through gen 2. Gen 1 was also locked to 5Gb/s just like 3.0.

What compression? USB doesn't have compression. The USB 3.x Type-A connector adds four pins to the USB 2.x Type-A connector to accomodate a single super-speed bi-directional (full-duplex) data lane. There are two pins for send and two pins for receive (shielded twisted pair differential signalling). The Type-A connector can support 5Gb/s and 10 Gb/s.

Posted by: Defoler

USB 3.2 allows two lanes through USB-C and compression, but the use of two lanes, is thanks to TB3. TB3 standard came out in 2016 from apple and intel, and the usb-c standard which came after was allowed through support from intel. So USB 3.2 was not driven by USB 3.1 but more by TB3 from intel and apple, who wanted USB-C hardware to be more common for apple.

When I said USB 3.2 is driven by USB 3.1, I meant that it uses the same speed 10 Gb/s but adds another lane. USB-C spec was published in August 2014. It had extra pins to support alternate modes such as DisplayPort alternate mode (published September 2014). Thunderbolt 3 alternate mode was announced in 2015. Therefore, the use of two lanes is thanks mostly to USB-C for supportting enough bi-directional data lines for future alternate modes and partly to Thunderbolt for being an example of a two lane bi-directional link.

Posted by: Defoler

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

What you are saying is that correct.
TB3 has 40Gb/s if you also account for the usb-c data reserves. It does indeed has 22Gb if you split and allow USB to transfer through it (which some of the cases do). But the standard allow non split data transfer, which allows full 40Gb/s connection.
That is part of the difference for example between the razer chroma core and the X. The X has a 40Gb/s hardware (I have seen a couple of youtubers actually testing it). It does not split and uses the full data lanes. So you are more limited by the data cables. The chroma has a split to data and usb in order to drive the ethernet and 4xusb connectors seperately from the PCIE data stream

What's a USB-C data reserve? Do you mean USB 3.1 gen 2 or DisplayPort? I have seen no benchmarks showing greater than 22 Gbps from a Thunderbolt port. Please post a link to an example showing otherwise. A cable either allows 20 Gbps or 40 Gbps - there is no other limitation caused by a cable (except PD). The Chroma uses a second Thunderbolt controller to handle USB and ethernet but that controller is connected to the first controller so they must share bandwidth to the computer.

We can try to get more than 22 Gb/s from a Thunderbolt controller by raiding two drives (one for each Thunderbolt port). When I tried that, I only got 23 Gb/s. Another option would be to try raiding a Thunderbolt drive with a USB 3.1 gen 2 drive, each connected to a different Thunderbolt port of the Thunderbolt controller. The raid would consist of three partitions on the Thunderbolt drive and one partition on the USB drive because Thunderbolt is over twice as fast as USB.

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Phoenix2063
(@phoenix2063)
Eminent Member
Joined: 3 years ago
 

So with USB 4 out in 2020, any sign of Thunderbolt 4? If so, expected bandwidth?

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Defoler
(@defoler)
Eminent Member
Joined: 2 years ago
 
Posted by: joevt

You said it was an upgrade of 3.2 as if 3.2 was getting new features. I called it a combination of 3.2 and Thunderbolt because the new features are from Thunderbolt and don't affect the 3.2 part.

At what exact point did I point or even hinted to new featurers?? I said, on my first post, the exact think you are saying now that you claim you contradict me, that USB 3.2 is upgraded with TB3, which is the added lanes.

I meant that the 5 Gb/s speed is from USB 3.0. Using dual lane (x2) is new to USB 3.2. I am confused by what you mean when you said "driven from TB3". Maybe you mean that the higher speed (dual lane) modes of USB 3.2 were created to compete with TB3?

Again, USB-C was developed for intel/apple TB3. The duel lane ability came from that connector along with TB3 specs. USB 3.1 was developed along side it, and with the help of the compression (or encoding, because it is actually data compression), it got the superspeed. 3.2 added the duel lane later on which was the base of TB3. So USB 3.1 and 3.2 were both spec driven by TB3.

What compression? USB doesn't have compression. The USB 3.x Type-A connector adds four pins to the USB 2.x Type-A connector to accomodate a single super-speed bi-directional (full-duplex) data lane. There are two pins for send and two pins for receive (shielded twisted pair differential signalling). The Type-A connector can support 5Gb/s and 10 Gb/s.

Encoding (it is a compression though). USB 3.1 allowed different encoding on the same data paths, which allowed 10GB/s. USB-C added the second lane that 3.2 uses for its duel lane. This was built first specifically for TB3. USB 3.1 was develop alongside USB-C, but they did not add the duel lane to it.

When I said USB 3.2 is driven by USB 3.1, I meant that it uses the same speed 10 Gb/s but adds another lane. USB-C spec was published in August 2014. It had extra pins to support alternate modes such as DisplayPort alternate mode (published September 2014). Thunderbolt 3 alternate mode was announced in 2015. Therefore, the use of two lanes is thanks mostly to USB-C for supportting enough bi-directional data lines for future alternate modes and partly to Thunderbolt for being an example of a two lane bi-directional link.

Using the same speed does not mean it was driven by USB 3.1. That standard was a result of encoding (or compresson) on the same data lines. USB 3.2 was driven by TB3 because of the added data lanes support to USB-C needed for TB3, which was developed alongside USB 3.1 (which didn't have alternate nor duel lanes) and alongside TB3 (for the 2015 macbook pro). Alternate mode was not part of USB 3.1 at all. USB 3.2 on the other hand has alternate mode because TB3 had it. While publishing time you are correct, you are incorrect on usage and development time and for.

What's a USB-C data reserve? Do you mean USB 3.1 gen 2 or DisplayPort? I have seen no benchmarks showing greater than 22 Gbps from a Thunderbolt port. Please post a link to an example showing otherwise. A cable either allows 20 Gbps or 40 Gbps - there is no other limitation caused by a cable (except PD). The Chroma uses a second Thunderbolt controller to handle USB and ethernet but that controller is connected to the first controller so they must share bandwidth to the computer.

I would recommend reading the TB3 spec sheet. Easy to find. TB3 data only (aka usb mode), is locked to 22Gb/s, yes. But in PCIE 3.0 data mode (not usb mode), it support more. From the datasheet:

Thunderbolt 3 uses PCIe x4 gen 3 data rate with 128kB header sizes. For a single Thunderbolt chip with two ports, the x4 PCIe interface data rate is shared across the ports. Two links of (4 lane) DisplayPort 1.2 consume 2x (4 x 5.4 Gbps) or 43.2 Gbps.

While chroma uses a second controller for USB, but it runs on a single TB3 connector, so it splits the TB3 data lanes to 18Gb/s and 22Gb/s, and because of that, unline the core, it limites you.

We can try to get more than 22 Gb/s from a Thunderbolt controller by raiding two drives (one for each Thunderbolt port). When I tried that, I only got 23 Gb/s. Another option would be to try raiding a Thunderbolt drive with a USB 3.1 gen 2 drive, each connected to a different Thunderbolt port of the Thunderbolt controller. The raid would consist of three partitions on the Thunderbolt drive and one partition on the USB drive because Thunderbolt is over twice as fast as USB.

What you are talking about is trying to run USB data stream on TB3 controler, which is incorrect to do. To run full 40Gb/s, you need to connect it to a PCIE hub, and put on that a drive. If you just connect data drives to it, they will be locked to 22Gb/s. But that is not the case with eGPU, since eGPU is run on PCIE, not just data stream.

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Defoler
(@defoler)
Eminent Member
Joined: 2 years ago
 
Posted by: Phoenix2063

So with USB 4 out in 2020, any sign of Thunderbolt 4? If so, expected bandwidth?

That depends if intel moves to PCIE 4.0 on their next iteration.
If it, there will be no TB4. It is based mainly on PCIE speeds and conncted to the CPU though PCIE lanes, so unless they get faster, and since intel aren't adding more PCIE lanes, it doesn't look good that TB4 will come out next year.

Intel's ice lake-sp (servers) is expected to have PCIE 4.0 in 2020, but the mobile version which were announced recently are not. They have TB3 only and PCIE 3.0.
And from intel's history, it most likely mean we won't see the refresh and PCIE 4.0 at least until late 2020.
AMD might drive intel to put their plans early with PCIE 4.0. Hopefully. But it might still not mean TB4. And if apple decide to shift to USB 4 on their next iteration, We might look for maybe 2021 to TB4.

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wimpzilla
(@wimpzilla)
Honorable Member
Joined: 4 years ago
 

To be honest i don't think the next iteration of TB have anything to do with the pci-e speeds.

If i recall correctly the main challenge for any wired connectivity are the wires themselves.
It is way more difficult to get reliable high speed communication between two devices linked by wires.
Rather than just upgrading the TB3 controller die with the new pci-e gen4 speeds.

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Eightarmedpet
(@eightarmedpet)
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Joined: 4 years ago
 

So Navi is announced... and @phoenix2063 prediction was pretty accurate.
I'm not overwhelmed - looks to be 10% performance increase for high TDP no Ray tracing (arguably not currently useful) and only about 50 USD cheaper (with Nvidia set to announce some weird update/price drop).

Anyone planning on getting one? Can't imagine Apple including them in their line up for about a year so macOS driver support will be an issue I'd guess?

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Phoenix2063
(@phoenix2063)
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Joined: 3 years ago
 

Thing to keep I mind is that enabling ray tracing on Nvidia cards cripples frame rates, even at 1080p which defies the point of buying a current generation card over a 10 series. Current gen just can't take advantage of it so just doesn't seem worth it for gaming imho.
As such Navi 5700XT with +10% perfoance over a 2070 is very relevent, also AMD seem to be looking at software options for Ray Tracing so may get that to a degree down the line. 

Imho current gen cards just can't take advantage of it so just doesn't seem worth it for gaming, especially as we're still struggling to get decent frames at 4k. 

Best to wait for independent reviews and overclocked 3rd party cards to land August/September. I have a freesync monitor that's not currently supported by Nvidia so would be interested in it.

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wimpzilla
(@wimpzilla)
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Joined: 4 years ago
 

Nvidia support VESA Adaptive Sync just fine, if i recall it properly.
Freesync is just a brand added on top of the VESA Adaptive Sync by AMD, i would suppose your monitor would works fine with Nvidia gpu's.

This post was modified 2 years ago

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E=Mc²

 
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Phoenix2063
(@phoenix2063)
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Joined: 3 years ago
 

Haven't checked on it in a while, from my understanding there's a limited selection of monitors it supports but would expand over time, last i check my Asus XG32VQ wasn't listed but may have been now. 

Been waiting for Navi before dropping money on the eGPU and the 5700XT is pretty much on budget for me and being AMD will give me less headache's that Nvidia for my Macbook. Also i'm mulling over building a gaming AMD Ryzen PC next year, depending on how the eGPU set up pans out, so in the long run an AMD card is my proffered choice. 

Side note to this being the AMD roadmap, it specifically stated we'd get 7nm+ Navi cards next year so i expect that'll be when they drop a Radeon 7 replacement. Potentially a dual GPU card given the recent Mac Pro card revealed, which i'd assume will help them reach 2080 & even 2080ti clock speeds (Radeon 7 does 'compete' with the 2080 in AMD friendly titles).

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