New system rendering much slower than the old one

[simon_english1]

I have just built a new system to replace my old one, having upgraded from a i7 8700k, GTX1060 with 16gb of ram to a i7 1200k, RTX3080 with 64gb of ram.

For some reason, while the V-ray benchmark tool is showing an increase in performance, when I render the same image from a project on each machine, the older machine is rendering considerably faster. Can anyone offer advice on on what may be causing this? Every other aspect of using the system and V-Ray seems faster it's purely CPU rendering that is coming out slower.

I have included some comparison times below as well as a screenshot of the V-Ray benchmark results. They are using the same files and rendering the same image on each machine without changing any render settings other than the output file name.

image number	New System Time	Old System Time
1	52:32 (minutes:seconds)	20:15 (minutes:seconds)
2	55:58 (minutes:seconds)	22:42 (minutes:seconds)

[^Lele^]

I'd guess the new system is overheating badly, and declocking as a result.
The benchmark is kept short on purpose, and as such the overheating isn't an issue.

[simon_english1]

I have a render running at the moment (one of the same images rendered previously. according to CoreTemp, CPU temperature is only around 27-37°C after 40 minutes of rendering.

[^Lele^]

Oh, then it could be the efficiency cores rendering, while the performance ones idle away.
I think it's an issue with the scheduling in windows 10, you may need to move to windows 11.
But hold on to the thought (of moving to win11) while i look for more solid data than my vague beliefs.

[^Lele^]

It seems i was recalling right.

Seems to be related to intel's thread director that is present in Windows 11 and not in Windows 10.
It's a windows 10 only issue.

Possible workarounds for win10:
*)Alder-lake Legacy compatibility for Windows 10 can be enabled in BIOS (f2/del) (should be tested).
*)E-Cores can also be disabled by Task Manager > 3dsMax > Details > Affinity > Uncheck e-cores.
*)Set program affinity to High (default is normal), for some apps. this will work to kick-in the e-cores.

Now, this stems from the fact that under host applications, we set the V-Ray rendering priority to low, so to not hog the host application unduly.
This isn't the case for the benchmark application, as its goal is to use all the resources at all times.

So, the simplest of *possible* fixes is to set the Max's priority to high in the task manager (there are freeware tools that can have that remembered and applied without manual intervention).
Try any of the other two if this one fails.
If all three are of no help, then the only solution for you would be to move to windows 11.

[simon_english1]

ah, thankyou I will give this a try.

Now I'm monitoring it more closely it does appear CPU utilisation only goes as high as about 22% when rendering, so definitely a lot of power there not being used.

[^Lele^]

Without endorsing anything officially, i have found great personal success with this little tool over the years.
See if it fits your bill as well.

[q976431]

I'm sure you need to upgrade to win11
Because I just did that
The problem of abnormal scheduling of 12th generation CPU has been fixed

[KiboOst]

Or fix it yourself : https://forums.chaos.com/forum/v-ray...31#post1143531