Hi,
Im testing Solaris and Karma before it gets used in production.
Im noticing a difference in the specular/normals when I use displacement.

Its just a megascans material with Albedo,Roughness,Normals and Displacement maps.
True displacement on with dicing 0.5.

Also with XPU, what is the VRAM load?
Load Memory : 4.98GB
Memory : 19.84GB
Peak Memory : 19.84GB

19.84GB RAM required to build the scene and 4.98GB VRAM to render it on the GPUs?

As a 1st post user, you might not be aware that those two render engines are not trying to be exactly the same. The fact you can A-B them is nice, but there are subtle differences.

The two engines are the most different in how they handle reflections and fresnel blending and roughness at glancing angles.

I do understand that the engines are different. I noticed that with XPU I hade to connect the MtlxNormal to the normalmap node and disconnect it for CPU to get the correct result.

Does XPU need more RAM to calculate displacement vs CPU? Nnoticed that I run out of RAM quicker with XPU in this scene.

Crosby
I do understand that the engines are different. I noticed that with XPU I hade to connect the MtlxNormal to the normalmap node and disconnect it for CPU to get the correct result.

Does XPU need more RAM to calculate displacement vs CPU? Nnoticed that I run out of RAM quicker with XPU in this scene.

That's bizarre! You shouldn't have to wire in Mtlx Normal (unless you need to feed in different normals or in different space) but more importantly CPU and XPU shouldn't interpret it differently. Can you please file a bug with an example scene? Thanks!

As for memory requirement... displacement on XPU *can* require more system RAM depending on how many per-point/vertex attributes the base mesh has, but if that's not the case the discrepancy is likely coming from elsewhere (or perhaps innocuous virtual memory usage).

Crosby
I do understand that the engines are different. I noticed that with XPU I hade to connect the MtlxNormal to the normalmap node and disconnect it for CPU to get the correct result.

Displacement is mutually exclusive with normal maps. There's no way to use it without importing the pre-displacement normal. The normal map is meaningless to the displaced normal, using both will result in a strange look.