C1 vers 6 sloooooooow on AMD Ryzen 7 + Radeon RTX 2060

I know I know, it's old software but... I installed my old copy of C1 vers6 on my new computer for some casual editing.

I find that it is extremely slow, in fact, it's impossible to work with. It takes in the order of 5 minutes just to start. Switching from one image to another takes in the order of 15 seconds or more. Making an adjustment works normally but then it takes between half and one minute to refresh the view.

It seems to be working mostly with the CPU, as it takes 10% while doing whatever it does (nothing externally visible). (The CPU has 8 cores)

I had it running well on previous computer, an Intel Core i7-3610QM

Just asking for the case anyone has a clue.

The computer is:

Win 10 Pro

CPU  AMD Ryzen™ 7 4800H

GPU: Radeon RTX 2060

RAM SDRAM DDR4-3200 16 GB

SSD 1 TB PCIe® NVMe™ M.2

And C1: Is Pro 6.6.4 64 bit

Cheers!