The latest versions of Panorama also support PAT where MTRRs cannot be set up properly.
I'd appreciate a less biased information flow.
To be more precise: PAT support is in GRADD.SYS which is used by Panorama.
want to draw your attention to a few points:
yes, the latest Panorama can use PAT to set WC for LFB, but Panorama tries to use PAT when it is not able to use MTRR - (I can hardly imagine when such a scenario may happen).
to use PAT or MTRR it is necessary to program corresponding MSRs and it is very important to have the same value in these registers between CPU cores, unfortunately, original kernel never offers an API to do proper MSR programing, that is why Panorama uses chain Panorama -> GRADD.SYS -> ACPI.PSD, this path does not give 100% guaranty that MSRs will be coherent (fortunately this missing coherency happens not very often, but I saw it a few times).
to use PAT Panorama (GRADD.SYS) hacks the PTEs corresponding to LFB (by the way SNAP is doing similar hack but for other reason). Yes it works and there is no other way to use PAT with original kernel - but me personally, I do not like such hacks.
os/4 kernel provides KernVMAlloc2 and a programer is able to set any type of memory caching without hacking PTEs, PAT MSRs are set during CPU start - this way coherency is provided.