After spending countless hours testing expensive video cards on the MSI X570-A PRO I have concluded there must me a whitelist as to what video cards will be allowed.
The PNY GTX 690 costs $999 and the Sapphire R9 Fury not much less. These two cards represent well over 12 TFLOPS of lost performance.
According to PC Part Picker, both video cards are claimed to be compatible. Not with my cards or motherboards. Suggests that this site needs some major work on it.
The PNY GTX 690 is a dual CPU card that implements SLI on the card. The refusal to operate suggests a whitelist and restrictive trade practices which would expose AMD and NVIDIA to a legal claim as this violates the Competition Act. Section 74(1) explains the exclusive dealing, market restriction and tied selling.
The old M5A99FX PRO R2.0 supported the GTX 690 fine. This motherboard has dual PCIe 2.0 x16 slots for video cards. This motherboard supports quad SLI and quad CFX with dual GPU cards.
What I do not understand is that the MSI X470 Gaming Plus handles the R9 Fury fine. The card obviously works and the BIOS is presented. It simply does not work with the MSI X570-A PRO.
So after retesting cards following a BIOS update I have reached the conclusion that there must be a whitelist.
I have seen whitelists extensively with Lenovo and Dell laptops but not with desktop motherboards which are supposed to be open architecture.
The old Lenovo T500 has an noncompliant WiFi card in it, so after the BIOS was fixed I installed a RTX8821 which works properly. Same story for my Lenovo T400 which also had the same noncompliant WiFi card. Intel technically owes me for the replacement WiFi cards.
Given the results I am now fearful of purchasing video cards given the 40% chance it will not work.
The PCI special interests group who develops the standard for all vendors to use says clearly that PCIe is backwards and forwards compatible.