Question:

Why is Thunderbolt 3 a rarity on desktop computers?

Jeremiah: 02 February 2022

Most recent higher-end laptops seems to have a Thunderbolt 3 connection. However, this does not seem to be case for recent motherboards or graphics cards for desktop computers.

I know that one application of Thunderbolt 3 is connecting external GPUs, which is a laptop-specific need. However, Thunderbolt 3 has other uses as well:

  • Seems to provide access to the PCI Express bus in general (although I do not know whether there is any other practical application for this than external GPUs).
  • Can provide a high-bandwidth video signal for external displays.

At least the latter would seem to be useful on desktop computers as well. Why is Thunderbolt a mostly laptop-only technology then?

Answer:
Anthony: 02 February 2022

It is not so much being a laptop-only technology but rather it just being that motherboards for desktop computers usually have multiple PCI-Express (https://en.wikipedia.org/wiki/PCI_Express) slots.

PCI-Express has many different hardware protocols (https://en.wikipedia.org/wiki/PCI_Express#Hardware_protocol_summary) and most motherboards for desktop computers often have;

  • At least one PCI-E x16/x8/x4 slot that is utilised by graphics cards, which already use the hardware standard outputs for current display input standards (HDMI/DVI-D/Display Port) and,
  • At least one PCI-E x1 slot for utilisation by storage expansions peripherals that use SATA Express (https://en.wikipedia.org/wiki/SATA_Express) or NVM Express (https://en.wikipedia.org/wiki/NVM_Express).