What are you calling the "scratch drive"? Is it a 2T M.2 NVME SSD or a 2T SATA SSD? Is this the D drive? What's the boot C: drive, NVME or SATA? If the scratch drive is a SATA SSD, it's relatively slow compared to an M.2 NVME SSD. So that could be part of your bottleneck. Suggest you run CrystalDiskMark (free) on your drives and compare speeds. An NVME SSD typically will have ~4-5x faster read/writes than a SATA SSD. If the boot C: drive is an NVME SSD, how big is it? You only have one NVME slot in the XPS 8940 but since NVME is faster than SATA, would it help to use the NVME SSD for the swap files, assuming it's big enough, rather than using what I suspect is a pokey SATA SSD for those files? Have you checked Windows to see how much of the 128 GB of system RAM is actually available? How much "junk" is running in the background that's hogging CPU/GPU time? BTW: When you installed that 2T SSD, was SATA Mode in BIOS set to RAID or AHCI? (Don't change the setting!)  Some SSDs (both NVME and SATA) may not work very efficiently when BIOS is set to RAID. There's an easy way to reconfigure Windows to allow BIOS to be changed from RAID to AHCI without reinstalling, but you have to do it the right way or you'll make the PC unbootable...
I have questions about processor upgrade for my 3D CAD/Rendering Workstation. I have an XPS 8940 currently running Core i7-10700 2.9GHz. RAM is maxed at 128GB w/ (4) 32GB DIMMs. PSU is 500w. Video is NVIDIA GeForce RTX 2060 12GB VRAM. Despite these good specs, the machine lags when working on very large models. I'm considering upgrading to this i9 CPU but I have 3 questions: 1. The increased number of cores should help with large models, but will the increase be noticeable or negligible? 2. The RTX 2060 draws 160w, and I read that this processor although rated for 125w can draw up to 200w+ under load. Will that leave enough power for other system components, or will this crash the machine all the time? 3. The current i7 came with a factory fan cooler. Will that be adequate for the i9 CPU or do I need a more powerful one?
XPS 8940, i9-10900K upgrade, #2