• From: Utah, USA
  • Registered: 2020-10-08
  • Posts: 104

Topic: UFX+ via Thunderbolt on PCH Lanes vs CPU Lanes

Is there anyone knowledgeable enough that can definitively state that there would or wouldn't be a difference when running a UFX+ via Thunderbolt direct to CPU vs Thunderbolt on PCH?

Looking to change a few components in my build but it would require that I move my Thunderbolt add in card to a slot that is on the PCH (shows this is supported in the manual), as opposed to the slot that it's currently in which is directly connected to the CPU.

Can't seem to find much information on this, I've heard whispers that in principle there is more "latency" on PCH lanes but that in practice there is no difference. The word latency, in the case of audio, is giving me major PTSD.

2x MADI FX | Digiface Dante | Fireface UFX+ | ADI-192 DD

2 Reply by ramses (edited by ramses 2020-12-01 08:03:59)

  • ramses
  • DAW Mastermind
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  • From: UTC+1
  • Registered: 2012-10-14
  • Posts: 12,869

Re: UFX+ via Thunderbolt on PCH Lanes vs CPU Lanes

This latency is not the RTL (Round Trip Latency) between recording interface and PC, its much lower inside of the machine.
The difference is that the CPU can't access the cards directly and needs to go through the connection between CPU and PCH. Its maybe compareable to add a 2nd switch to your network. When the switch interconnect is properly sized you will recognized merely a difference.

I also prefer PCIe sockets with PCIe lanes coming from CPU, because these are also quicker, in my case PCIe 3.0 vs PCIe 2.0. But if you connect only a few things to Thunderbolt then it shouldn't make a big difference. Recording Cards do not have very high requirements in terms of PCIe lanes. If I remember right the RME PCIe cards work even with PCIe 1.x.

At the end you need to try out, because I remember mainboards where it was critical, which PCIe socket you choosed to place a PCIe firewire card. And you also need to honour, that with some mainboards PCIe lanes might be shared between a PCIe socket and another component. This is usually the case, if the CPU can not deliver enough PCIe lanes (depends on the mainboard design, for this you need to look closely into the manual).

BR Ramses - UFX III, 12Mic, XTC, ADI-2 Pro FS R BE, RayDAT, X10SRi-F, E5-1680v4, Win10Pro22H2, Cub13