Comment by lapetitejort | Hacker News Reader

Comment by lapetitejort | Hacker News Reader

Back in the tail end of 2019 I tried to go full Thunderbolt 3 (T3 from now on). I wanted to swap between my desktop rig and MBP '19 with just a single wire. I bought a T3 dock and prepared. Problems:

1. Nvidia RTX 2070 does not support T3. I could not use a T3 dock at all. Regular USB C docks could connect to the card and run everything else though.

2. My MoBo did not support T3. Not only would I have to upgrade it, I would also have to buy a PCIe card and use short DisplayPort cables to connect the graphics card to it in order to have video out.

So I downgraded to a USB C dock. More problems:

1. My MBP '19 only allowed one monitor to connect. But I had a few year old ThinkPad that could drive two monitors!

2. The keyboard connection started to become unreliable. So I hard-wired it to the desktop.

3. Eventually the MBP stopped outputting video to the monitor. Apple said I had to update the firmware in the monitor. I declined.

Eventually I gave up on docks. The USB C dock now acts as the most overpriced dock imaginable for a ChromeCast '20. Maybe one day I'll try with Thunderbolt 4 with plenty of planning beforehand. Or maybe not.

The single monitor thing is because apple doesn’t support DisplayPort MultiStream. It has long been confusing why because pre apple silicon it worked fine on their GPUs in windows but macOS has no support. Given their thunderbolt drive it seems silly.

This is a long standing flaw of macOS. The common workaround is a lot of these docks will offer a TB3 passthrough, where a standard USB-C to whatever-you-need, will work.

That, and the issue where your Nvidia graphics card simply won't work over Thunderbolt 3 (or at all, for that matter). It's a long-standing and frankly petty omission that really leaves me wondering how serious ML researchers get their work done on the platform...

I've recently tried this. It's not much improved. I have a PC, and invested in the TB3 compatible motherboard and add-in card. Displays rarely work, but so I instead hardwire this machine to the displays, as they have the extra inputs. On some boots, Thunderbolt isn't detected and will need a few reboots to be picked up. Getting the drivers installed, for a custom build PC, was also a nightmare. The thunderbolt headers are unique to manufacturer, so my Gigabyte Titan Ridge has a 5 or 3pin connector, whereas my Asus board is a 12 pin. Luckily, it seems to only be present for DMA security, so if you bridge pins 3 and 5 on the Add-in card it works. The motherboard still needs to support thunderbolt however, this didn't work on an older, z270 chipset.

On the MacBook side the only issue is that when disconnecting, a display won't sleep and just show a frozen image.

So, at least rest well knowing you've cut your losses wasting time with thunderbolt.

In my experience, boards with built in TB work better than boards that have headers but require a dedicated card.

Recently I put an ASUS ProArt X570 Creator in my main tower, and its onboard TB4 works great. Some basic functionality was there straight away after a clean Windows install and the gaps were filled in by installing Thunderbolt drivers from ASUS’ support site for the motherboard. It even supports G-Sync on the monitor through the hub-connected monitor, which was a real surprise (though refresh rate is limited to 120Hz without using a compressed color format due to the dock only supporting DisplayPort 1.2).

The biggest problem was actually getting the video card to recognize DisplayPort as a monitor connection during boot. For some reason EVGA 3000 series cards had a quirk where DP connected displays weren’t recognized in EFI and would only come online after booting the OS. Thankfully EVGA had a VBIOS update available that fixed this.

I’m looking forward to more TB4 docks being released. My current dock, the TS3+ has been quite reliable (especially after updating its firmware), but as noted its DP out is outdated.

Oh no doubt. To be clear, mixing and matching manufacturers was a cost-saving measure, and in retrospect, should have done better research.

I did eye the ProArt board, but considering it was over twice as expensive in my region for a machine not really intended for content creation, i went with the far cheaper option.

Also using the CalDigit TS3+. Fantastic dock.

I just installed a Thunderbolt 4 card in a new motherboard, so I'm being a little more optimistic, but I will take advantage of the free return policies over the holidays if necessary. The only problem I have is devices from my connected Thunderbolt 3 dock stop working after waking from suspend (but the display DOES work), so I'm going to try updating drivers to see if it works.

Essentially I have the solution you desired to set out to achieve, just through lucky choice of base hardware - single cable from desktop/laptop to dock which carries two monitors, keyboard, mouse, audio and network.

This stemmed from a hatred of USB-C Docks - I was provided a low end mac laptop for work and a usb-c dock with a DisplayLink chipset in it to drive two monitors on my desk. This was so lacking in performance there was visible lag on the desktop as the dual core processor was completely swamped having to render 2x1080p displays entirely in software. Basic tasks were unacceptably slow, the machine was demonstrably faster on battery than it was plugged into this dock and receiving power. I self funded a Caldigit TS3+ dock and immediately could use the laptop as it should have been in the first place, we got immediate approval to expense a purchase of these for the whole team. and I brought my dock home.

I have a HP Workstation as my desktop and the official method for supporting Thunderbolt 3 is exactly as you describe, install the add in card, use the two short DisplayPort Cables to the DP Inputs on the Thunderbolt card, and to then use the single cable to connect to the dock. GPU Display Out -> Thunderbolt PCI-E -> Dock. This appears to be the scenario for all desktop PCs using Thunderbolt, even the computers with the chipset built into the board - there's always a DisplayPort Input involved to present the display output from the GPU to the target.

On the counter side to this even Apple who are all in on Thunderbolt have problems with this separation between Display and PCI-E - If you look at the Mac Pro they've done some serious work with their custom PCI-Express implementation in the form of their MPX extensions to enable Thunderbolt support through their GPUs, by the looks of things they do the opposite thing - essentially routing PCI-E through the GPU and out of the USB-C ports on the GPU.

As an aside - nVidia discontinued USB-C Ports on their GPUs with the next generation 3000 series, this I think will lead to less confusion going forward

GPU and Thunderbolt compatibility is not a thing. Thunderbolt exposes the Raw PCI Express lane (in or out I guess).

Your laptop or motherboard might not, but many of us over on egpu.io have used all recent a videos cards over Thunderbolt just fine.

I have a GTX 1070 in a egpu box , connected to a dell xps 9370, works perfectly.

GPU and thunderbolt compatibility most definitely is a thing when your GPU has a type-C connector on it and you're trying to use that connector for thunderbolt.

it's definitely a thing and it's definitely always "not compatible."

Ohh, he is literally talking about a USB-c port on the back of the graphics card. That port isn't Thunderbolt, nor has it ever been advertised as such. It's a weird port meant for Virtual Reality....so yea not sure what to say about that.

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