Thunderbolt implementation on AMDs B550 chipsets

FinOxy · May 7, 2021

Hi everyone
I was looking at my ROG B550 boards manual. There seems to be thunderbolt header, for a PCIE-add-in card. From what I have gathered, it is the same used with Intels other chipset.
The funny thing is that B550 chipsets PCIE connectivity is limited. If I have understood correctly, there is 4 PCIE 3.0 lanes coming off the chipset, which are spit up for many different places, like the 2,5 Gigabit intel ethernet, the secondary PCIE 16x slot, and the couple PCIE 1x slots. And the second m.2 drive slot, which in use disables also 2 of the sata III ports. I guess I could run a SATA M.2 drive on there, and have a secondary devices using the other lanes, but that would be in the same area of just connecting a 2.5 ssd with a SATA-cable.

This would mean that if you wanted to deploy that TB-header, (the card that you need to use to get to actually use it is called ThunderboltEX by ASUS. ), you would lose all or at least large part of the Chipsets PCIE bandwidth. And from what I have seen on the internet, ASUS has not implemented TB-3, or as it should be called in this case, USB-4, greatly. It does come with a cable in the box for display-in, but it also takes a USB-2.0 connector, and in 2 port variant, a 6-pin power cable.
Do you know, if there is other OEMs other than ASUS doing this?
And what do you think of the actual usefulness of the add-in cards, and their limiting of the expansion of a system in the future?

riklaunim · May 7, 2021

Gigabyte also has such card. By default your x16 slot for GPU would work as x16 4.0 but if you add second NVMe drive or second PCIe device it will be bifurcated - the GPU will drop to x8 4.0 (so x16 3.0) while the new device will get what it's asking for. As there are no GPUs that need x16 4.0 you should not see any performance penalties.

ki8aras · May 7, 2021

honestly from personal experience in the past, the most useful use case for thunderbolt is external storage or external gpus, obviously external gpus arent needed in a desktop and usb 3.2 has mostly taken care of my needs for super fast external storage. what im trying to say here is that the extra cost and hassle of implementing it isnt really worth it in a desktop system and thats why most manufacturers have refrained from implementing it

FinOxy · May 7, 2021

8 minutes ago, ki8aras said:

honestly from personal experience in the past, the most useful use case for thunderbolt is external storage or external gpus, obviously external gpus arent needed in a desktop and usb 3.2 has mostly taken care of my needs for super fast external storage. what im trying to say here is that the extra cost and hassle of implementing it isnt really worth it in a desktop system and thats why most manufacturers have refrained from implementing it

Yeah, I was thinking of the mostly same thing
I am personally on the jurastic period where usb 3.0 and dp 1.2 are honestly good enough
As well as VGA