Since the introduction of AMD's Smart Access Memory (SAM) technology we've heard that this technology isn't limited to AMD's latest platforms as the technique is part of the PCI Express specification. Motherboard makers are starting to enable Resizable BAR for Intel motherboards and NVIDIA is also looking into getting it to work for its GPUs.
Interestingly, it seems Resizable BAR will work better on older Intel platforms than on AMD's previous generations. TechPowerUp reports AMD's Zen 2 (and older) do not support the feature due to hardware limitations. Support for the necessary PCIe feature didn't get added until the Ryzen 5000 "Vermeer" lineup as older Zen generations do not have support for a feature called "full-rate _pdep_u32/64".
Intel processors on the other hand have had support for this feature since the Haswell generation, so basically since 2014. At least in theory, every Intel platform since the 4th Gen Core can support Resizable BAR should motherboard makers release BIOS updates for this.
