About a year ago I installed a Nvidia GTX 2060 video card with 1,920 Cuda cores to speed up my dual processor workstation and I immediately noticed an improvement with several programs including DPP. I also found that my 1DX III is even more demanding than the prior 1DX models in terms of file processing and this is on a fast workstation with two Xeon 8 core (server quality version of the I7) processors and 128 gigs of memory per CPU. I noticed that recently the file conversion was taking longer than the 2 seconds or so that I had grown used to and while watching task manager even when not much was going on, GPU loading was spiking to 30% with just regular Win 10 processes.
The base problem is with the Nvidia driver/settings default which even in a desktop or workstation sets the Nvidia card to power conserving mode. To fix this issue, open Nvidia settings, with Windows 10 use the show hidden icons up arrow which appears on the right bottom corner of your desktop. Click on the Nvidia settings icon and click manage 3D settings under the 3D settings menu section. Choose the global settings tab and click power management mode, it is around the bottom 1/3 of the available settings and choose prefer maximum performance. You now have any program set to use Nvidia global settings to use maximum performance mode which allows the display adapter and its GPU/shader cores to run at maximum performance which will take more power.
There is one additional step you will probably have to do. Choose the program settings tab next and if Canon DPP isn't on the list then use the add button to add it to the Nvidia managed programs. Once added, change DPP to use Nvidia global settings. Do this for any other program that you want added to this performance level that isn't already in the Nvidia list.
After allowing my 2060 to run at full performance mode, GPU usage under regular windows stays under 4% instead of spiking to 30% or higher and DPP is back to full speed. Task manager has issues with how it displays the computers functionality because even when resources aren't near the 100% utilization level, there is still a slowing as the percentage goes up. The 2060 is a high performance card and even though it never went past 40% in DPP along with the other Windows processes it was still slowing the system when it was performance limited in the Nvidia power management settings.
Caution: If you are running a laptop then you may not want to make this change because it will increase power consumption not only reducing battery life but some included laptop adapters/chargers are running near their limit in normal use and may run hot if you allow the card to constantly run at full power. And if you are running a high performance card in a system with minimal cooling or power supply ability, this will stress it further. My workstation has 13 fans total and a 1,275 watt power supply so it is running well within it capabilities and the only time the fans are commanded above idle speed is when rendering large 4K video files but consider using a program like the free HWinfo to monitor thermal behavior of your system if running a high performance card in a system that is near its limits. I left the Nvidia settings at their normal level in my HP Zbook laptop "mobile workstation" because I don't use it at levels where full performance is needed even though it is theoretically designed for that sort of service.
You are welcome and with Windows 10 we all have to follow the mission statement of the university where I taught before retirement which stated our students would spend the rest of their lives learning. I was a bit dubious about that statement because it sounded like we were doing such a lousy job of preparing the students that they would spend the rest of their lives making up for the deficit. It is akin to the poorly designed slogan used by one of the global airlines in the 1970s that invited its passengers to "learn to fly with us", I prefer traveling on a carrier where the crew has already learned how to fly the plane 🙂