Titan Ridge's HBR3 lanes count

[londbell]

With Intel's Datasheet:

Compare to old generation Alpine Ridge,Titan Ridge support DP1.4(So it can run dp links on HBR3);But it seems that Titan Ridge only can hold 4 HBR3 lanes.

4 HBR3 lanes:25.92Gbps
8 HBR2 lanes:34.56Gbps
XDR@6K 10bit 60hz:36.644Gbp
So for Pro XDR@Thunderbold3,it should be no different between Alpine Ridge and Titan Ridge(They can only combine 8 lanes HBR2).But apple announced the compatibility:

It seems that Titan Ridge based mac(without navi gpu) also can push xdr to 6K.I am so confused.Titan Ridge can just combine 4 lanes HBR3,and that is less then 8 lanes HBR2.

 

[joevt]

With Intel's Datasheet:
View attachment 899533
Compare to old generation Alpine Ridge,Titan Ridge support DP1.4(So it can run dp links on HBR3);But it seems that Titan Ridge only can hold 4 HBR3 lanes.

4 HBR3 lanes:25.92Gbps
8 HBR2 lanes:34.56Gbps
XDR@6K 10bit 60hz:36.644Gbp
So for Pro XDR@Thunderbold3,it should be no different between Alpine Ridge and Titan Ridge(They can only combine 8 lanes HBR2).But apple announced the compatibility:
View attachment 899535
It seems that Titan Ridge based mac(without navi gpu) also can push xdr to 6K.I am so confused.Titan Ridge can just combine 4 lanes HBR3,and that is less then 8 lanes HBR2.

Apple has driver or firmware to allow dual HBR3 from Titan Ridge to Apple Pro Display XDR. Blackmagic eGPU had a recent firmware update to enable this (it also uses Titan Ridge). Dual HBR3 probable won't work from Windows or PCs.

Dual HBR3 over Thunderbolt 3 is possible for 6K because 6016x3384x60Hzx30bpp = 36.64 Gbps < 40 Gbps and the DisplayPort stuffing symbols used by DisplayPort to fill up the HBR3 bandwidth are not transmitted by Thunderbolt - they are recreated when a Thunderbolt controller converts the Thunderbolt DisplayPort packets back into a DisplayPort signal (inside the XDR display).

You can read about DisplayPort tunnelling in the USB4 spec (DisplayPort In adapter, DisplayPort Out adapter, registers for local capabilities, remote capabilities, and common capabilities).

I have some Titan Ridge devices that allow 4 lanes of HBR3 with 4 lanes of HBR (similar bandwidth to 8 lanes of HBR2) but I can't get dual HBR3 - I would need to make a patch to the driver or firmware somehow.

 

[londbell]

Apple has driver or firmware to allow dual HBR3 from Titan Ridge to Apple Pro Display XDR. Blackmagic eGPU had a recent firmware update to enable this (it also uses Titan Ridge). Dual HBR3 probable won't work from Windows or PCs.

Dual HBR3 over Thunderbolt 3 is possible for 6K because 6016x3384x60Hzx30bpp = 36.64 Gbps < 40 Gbps and the DisplayPort stuffing symbols used by DisplayPort to fill up the HBR3 bandwidth are not transmitted by Thunderbolt - they are recreated when a Thunderbolt controller converts the Thunderbolt DisplayPort packets back into a DisplayPort signal (inside the XDR display).

You can read about DisplayPort tunnelling in the USB4 spec (DisplayPort In adapter, DisplayPort Out adapter, registers for local capabilities, remote capabilities, and common capabilities).

I have some Titan Ridge devices that allow 4 lanes of HBR3 with 4 lanes of HBR (similar bandwidth to 8 lanes of HBR2) but I can't get dual HBR3 - I would need to make a patch to the driver or firmware somehow.

I knew your calculation and i support that.But i am so confused about intel's datasheet

 

[joevt]

I knew your calculation and i support that.But i am so confused about intel's datasheet

Those aren't real data sheets - you don't get to see those unless you're a Thunderbolt product developer. What you see is mostly just marketing materials. They aren't wrong - just incomplete:

So "8 HBR2" is correct (8 lanes * 5.4 Gbps * 8b/10b = 34.56 Gbps).
And "4 HBR3" is correct (4 lanes * 8.1 Gbps * 8b/10b = 25.92 Gbps).
But "4 HBR3 + 4 HBR" is more correct (4 lanes * (8.1 + 2.7) Gbps * 8b/10b = 34.56 Gbps).

At https://en.wikipedia.org/wiki/DisplayPort , it says "Unlike DVI and HDMI, which vary their transmission speed to the exact rate required for the specific video format, DisplayPort only operates at a few specific speeds; any excess bits in the transmission are filled with "stuffing symbols".

At https://www.usb.org/sites/default/files/D1T1-3 - USB4 System Overview.pdf , it says "stuffing symbols not sent"

This is sort of hinted at by https://thunderbolttechnology.net/sites/default/files/Thunderbolt3_TechBrief_FINAL.pdf which says "After the link is established, Thunderbolt only transmits the display traffic as demanded, so even though about 17 Gbps of available data bandwidth is needed to setup a DisplayPort 1.2 connection, if the screen resolution is set to 1080p, only ~4 Gbps of the Thunderbolt link is used for display. If it is a 4K display, perhaps 14 Gbps will be consumed depending on the exact pixel count, color depth, and refresh rate."

Taking those statements together: it means "8 HBR3" is 51.84 Gbps (8 lanes 8.1 Gbps * 8b/10b) but if you only need 36.64 Gbps (like for 6K) then much of the 51.84 Gbps is "stuffing symbols" which Thunderbolt does not transmit (same as USB4). Instead, Thunderbolt recreates the "stuffing symbols" at the DisplayPort Out Adapter.

Apple's driver or firmware can make their Titan Ridge controllers transmit 6K using dual HBR3 probably by modifying the DisplayPort capabilities registers (mentioned in the USB4 spec and the Linux kernel driver for Thunderbolt 3).

 

[londbell]

Those aren't real data sheets - you don't get to see those unless you're a Thunderbolt product developer. What you see is mostly just marketing materials. They aren't wrong - just incomplete:

So "8 HBR2" is correct (8 lanes * 5.4 Gbps * 8b/10b = 34.56 Gbps).
And "4 HBR3" is correct (4 lanes * 8.1 Gbps * 8b/10b = 25.92 Gbps).
But "4 HBR3 + 4 HBR" is more correct (4 lanes * (8.1 + 2.7) Gbps * 8b/10b = 34.56 Gbps).

At https://en.wikipedia.org/wiki/DisplayPort , it says "Unlike DVI and HDMI, which vary their transmission speed to the exact rate required for the specific video format, DisplayPort only operates at a few specific speeds; any excess bits in the transmission are filled with "stuffing symbols".

At https://www.usb.org/sites/default/files/D1T1-3 - USB4 System Overview.pdf , it says "stuffing symbols not sent"

This is sort of hinted at by https://thunderbolttechnology.net/sites/default/files/Thunderbolt3_TechBrief_FINAL.pdf which says "After the link is established, Thunderbolt only transmits the display traffic as demanded, so even though about 17 Gbps of available data bandwidth is needed to setup a DisplayPort 1.2 connection, if the screen resolution is set to 1080p, only ~4 Gbps of the Thunderbolt link is used for display. If it is a 4K display, perhaps 14 Gbps will be consumed depending on the exact pixel count, color depth, and refresh rate."

Taking those statements together: it means "8 HBR3" is 51.84 Gbps (8 lanes 8.1 Gbps * 8b/10b) but if you only need 36.64 Gbps (like for 6K) then much of the 51.84 Gbps is "stuffing symbols" which Thunderbolt does not transmit (same as USB4). Instead, Thunderbolt recreates the "stuffing symbols" at the DisplayPort Out Adapter.

Apple's driver or firmware can make their Titan Ridge controllers transmit 6K using dual HBR3 probably by modifying the DisplayPort capabilities registers (mentioned in the USB4 spec and the Linux kernel driver for Thunderbolt 3).

Thanks!