Hi and welcome to this forum

Hate to be the bearer of bad news but... I don't think TB4 will work, you need TB2 or TB3. So unless your laptop also has an Express port which accepts an approved PCIe to firewire card you may want to find one that does.

As for upgrading you already saw that that's a delicate process in at least two steps. Personally I would only attempt it with a Windows 7 laptop because it allows you to first make 100% sure that the firewire connection with firmware 1.12 and old UC is working fine. You simply can't risk any issues during the upgrade process. And yes, you do want 1.7.6 on the mixer to use it with Windows 10 eventually. So... old W7 laptop with Express port... approved PCIe to firewire card (which you can use in the old laptop and in the newer one)... and an empty agenda. You don't want to rush this!

I appreciate the information, even if it wasn't what I expected. Looks like I'm out to find a Macbook Pro with firewire port.

So the firmware/Control center upgrading is probably different? I couldn't find a specific article for upgrading that using a Mac.
From what I have read, looks like Mojavi is the latest version you can go. Is that correct?

Perhaps not. As I remember it, upgrading from 1.2 to 1.3 using a Mac is a fail. Windows 7 was the safer path.

Alright, so I decided to tackle the Update on my SL 1642 using a Windows 10 Professional computer. My original firmware was 1.12

I used an approved firewire PCIe card and I know it works, since I've been running other firewire interfaces successfully with it. I'm also up to date on all Windows 10 updates.

The instructions for doing this are here: https://answers.presonus.com/243/update ... ns-earlier

Here's what I did once I installed the UC 1.2 -
Right click on the launch icon and choose properties
Select the Compatibility tab
Click "Run this program in compatibility mode for:"
Select "Windows 7" from the drop down box.
Also click the "Run this program as an administrator" box.
Click Apply.
Click OK

On the mixer, in system settings, be sure that the device ID is set to 0 (zero). Otherwise, the mixer and computer won't see each other.

I then rebooted the PC and then launched the UC 1.2 program. Started the mixer. They saw each other and then in UC I chose the firmware selection. Firmware updated and I just followed the on-screen instructions.

From here, I just followed the instructions in the link listed above. My mixer is now up to date and ready to roll. This all went super smooth!

I hope this helps others who may be in a similar situation(s).