Thunderbolt is an awkward implementation, but a good product. There is no alternative offering that provides what it does.

Reading the rant you linked, there seems to be no real content or references to information. It mostly complains about USB-PD negotiation of the Thunderbolt alt-mode (which doesn't have anything to do with thunderbolt), and that the controller is proprietary (which sucks, sure, but so is most other controllers in the system).

IOMMU not being on by default as it should be is a motherboard manufacturer problem. Vulnerabilities found with it active should have CVE's created so that they can get fixed, like any other safety issue.

As someone using Thunderbolt on my Linux laptop, I can inform you that it works quite well.

(EDIT: Also note that Intel technically has promised to make Thunderbolt open and royalty-free, although they have missed their deadline on that promise.)

I mean, I want 10 gbit+ peripherals and short of using PCIe extenders, what choice do I have? USB 3? Wait no, USB 3.1 gen 1, wait no USB 3.1 gen 2! (Yes, I know there's different Thunderbolt versions, too).

If Dell's going to do silly things like solder Wifi chips down on the new laptops, then you're damn right I'm going to be looking for Thunderbolt for fast connectivity out of a very expensive laptop.

…renamed to USB 3.2 gen 1, 2 and the upcoming 2x2 as of yesterday.

What we really need is USB 4.7 gen 1.2^3

What was the motivation for building it this way, instead of by more directly exposing PCIe? There must be some upside to they way it’s designed, no?

PCIe as a phy is not designed for long distances or complex topologies. A lot of motherboards, including high-end server boards, cannot even route the PCIe lanes from CPU to PCIe socket without there being connectivity issues, which manifest as things like PCIe retransmits (which result in plummeting performance).

Designing a purpose-built phy/mac, designed to handle long links and complex topologies, is the obvious thing to do.

I think to have the flexibility to have various topologies of many devices (daisy-chained, etc.) from a single port.

Probably also timing etc. - I would think making it packet based is probably easier to make work over longer cables than raw PCI-e.

The bit I really don’t get is why they keep all the specs secret. What do they think they have to gain? All that it has meant is less adoption...

PCIe is also packet-based BTW [1]. The benefit from the custom protocol is being able to run PCIe and DisplayPort (and I guess networking which no one cares about) over the same cable at the same time with dynamic bandwidth allocation. USB-C has alternate modes but they're not as powerful. In theory PCIe alternate mode over USB-C should be possible and it would be much simpler than Thunderbolt but nobody has tried to build it.

I imagine the spec doesn't really exist because Intel has been too lazy to properly write it (I wouldn't be surprised if Thunderbolt is basically defined as whatever the original Ridge controller implemented) and it's probably also gross. Adoption seems to be limited by cost, not by secrecy (thinking back to Firewire, it was open but there were very few controller chips for it).

[1] Check out PCIe over RS-232: https://www.youtube.com/watch?v=QMiubC6LdTA

> What was the motivation for building it this way, instead of by more directly exposing PCIe?

I think when intel was doing Light Peak, they didn't have IOMMU, which in my limited knowledge seems to be a solution to at least some of what is wrong with normal hot plugging PCIe (aside from somewhat complicated hardware design, I imagine). Of course IOMMU was clearly never implemented correctly, so all was for naught.

But there's no alternative.

USB

USB has more more limited bandwidth constraints and, IIRC, has much higher CPU overhead and overall higher latency.

It also just can't do things that Thunderbolt can. TB to the end user is a free PCIe slot for Firewire, 10GbE, eGPU, etc. The fastest USB can't do that. I get that it has issues but it's still incredibly valuable.