It is supported on your GPU with both 3000 and 5000 CPUs
check your motherboard manufacturer to see if it is available. If it is an older mb it will likely not support it at all or you may get lucky and just need a bios update. Once you determine if your motherboard is compatible follow an enabling guide for your specific mb manufacturer. The enabling process is he same as a 6000gpu with a 5000cpu. I would tell you how but it’s different for every mb manufacturer. Once you have enabled it via bios, you can check to see if it is working by going to control panel open device manager click on your GPU in display adapters. Go to properties then resources tab. And if it says “large memory range” then it’s successfully enabled. You more than likely will see little to no difference on the older architecture. But many games will have single digit percentage performance increases. Some will have decreases too lol.
Sorry folks. SAM and Resizable Bar may be enabled on your system's bios, but the AMD RX-5700XT cannot make use of it, because it DOES NOT have the HARDWARE available in the card.
On the first page of GPU-Z, "Enabled" listed here is only a report that the Resizable Bar is available and configured in the bios.
If you move to the "Advanced" tab, and select "PCIe Resizable Bar", you will see that there is NO "GPU Hardware Support" and there is NO "Graphics Driver Support" on the RX-5700XT.
All of the options in the "Red Box" are a report on your systems's bios readiness to support a Resizable Bar. These should all say "Yes" if you have the Resizable Bar correctly configured on your system.
In conclusion, the Resizable Bar may be available on your system's motherboard, but it is "NOT Available" on the RX-5700XT because there is no "Hardware or Driver" support for it.