Hi Bob,
step by step:

1) Set thumb quality to best by using menu item set to Best Thumb Quality See screen snap 005.
2) Now do a rebuild of thumbs in current folder using Select all and rebuild selected. see Screensnap 007
3) If all is well, you can continue to do each folder, or use screen snap 006 to redo them all.
4 When doing 007, say hello to "James"
Fred

Bob, the explanation is straightforward.
First of all, TIFs and PSDs are larger files. They will take longer. JPGs and Raws are  more reasonable in size. (Assuming you have a reasonable number of Pixels per shot)
The rebuild in your case involves deleting the old thumbs and rebuilding new ones.
The task is CPU intensive and is a one time build.  Qimage is building more than thumbs, but the cache files that go with each image. Once done, they stay with your images.

You can improve your wait time by Using the selection in the drop down menu from Thumb Cache folder, RAW only or new raw only.

I am curious to know the pixel dimensions of your images. You might have one of those NIKONs with a 75 megabyte image file and a 36.3 Mega pixel size, and that would take a while.

Repeating the main point, QU is building high Quality cache files along with the thumbs. This is the important fact to keep in mind since it is a one time build, and contributes to te extraordinary quality I get from Qimage.

Hope this helps.
Fred

Fred
Sorry for the delayed response.
The core settings recommendation was a help - a little quicker.  Thanks
I am one of those with a Sony and 42mp files - actually closer to 80 on disc.  I have set the file types to only TIFF and PSD as I don't print raw or jpeg.  I only use QU for printing.
Interesting that it renders the files so much slower now than it did before the reinstall of Windows and QU.
I am pretty tech savy, however, I did miss the multicore setting in QU and it is possible I have missed something somewhere else.  I will keep looking.
I am used to Capture One rendering my raw images in 1 - 2 seconds even for the large raw files.  As an example the day before I posted the original thread I ingested 243 42Mb files (81-83 on disc) and CO rendered all 243 to highest quality 2560 in just under 5 minutes.  I tested QU for raw renders for the exact same 243 images and it only took 27mins 34 seconds - there were no tiffs, jpegs or psds.  This was before reset the multithreading - I am going out tomorrow and will test my days shoot and see if it is just as slow - I expect not.
Thanks so much for your help
Bob

That's what I was thinking.  I don't think it's actually developing the raws if it only takes 1-2 seconds.  Capture One might just be pulling the embedded JPEG from the raw.

Regards,
Mike