intel xeon and light cache

hi, i have recently switched form i7 5820k to a single xeon e5 2686 v3, and whitchever scene i open and try to renderer the light cache takes forever. never had problems with my 5820k, where light cache took mostly few minutes. does it have anything to to with clock speeds or core count? I heard something that i should set light cache passes equal to the number of cpu threads but there's no such setting in vray any longer, or i cannot find it. vray 3.4 and 3dsmax 2016. thanks in advance

edit: displacement, dinamyc memory limit or defective material isnt an issue here, since it renders ok with 5820k

There is a tax that you need to pay when you go to multi CPU with lower clock speed. I remember there was a problem also with VRay and large core counts but I believe it been fixed in the latest release.

Over all more cores will render faster but single thread functions will always limited by the clock speed.

Check your displacement memory consumption, maybe you are running out of RAM. Light cache is not friendly with displacement.

is light case based on single core?

displacement is disabled ant system utilizes ~70% of available ram white calculating ligh cache. I tried swithing off forest pack layer with all vegetation with it, and it managed to finish ligh cache in ~6 minutes which is acceptable (3400x1600), so o suppose it has something to do with large amounts of proxies/geometry

i just hope there's some wrong setting waiting to be adjusted to make it work as its supposed to :|

Light cache is multi threaded, but it can grow on memory usage with too many displacements (or detailed displacement) or large amount of fine geometry such, Trees and grass.

For exterior I would go Irradiance-Brute force instead or just Brute force-brute force.

having said that you could try to uncheck retrace and pre-filter.

also reducing the number of bounces may help, 50 should be fine, default is 100

You could also try to change your dynamic memory, this will depend of how much memory you have.

https://knowledge.autodesk.com/support/3ds-max/learn-explore/caas/CloudHelp/cloudhelp/2016/ENU/3DSMax/files/GUID-5F506D3B-BC0F-4605-8EE5-A294543C0C1F-htm.html

Multi-threading is ON in render settings? Check it, never knows...

I agree with Francisco, if I have an issue with Lightcache taking too long then normally increase the dynamic memory and it clears up. By default it's 4000mb, try to increase to 6000 or 8000. That should handle it (Dynamic memory limit is in the render setup, settings tab).

If the dynamic memory limit is too low your machine will be loading and unloading geometry while trying to do the lightcache and it will slow down the light cache to a crawl.

thanks for your help, reinstalling of vray helped:)