Core, blimey!

[#1]

I currently have two programs running rendering various video files to reduce their size. Running overnight was fine but now I am finding, with all 6 core, at 100% most of the time, other things can grind to a bit of a crawl occasionally.
Pausing isn't possible at this stage and there's, maybe, 5 or more hours left to run.
The two programs are DivX Plus Converter and Handbrake. What are the possible outcomes of right-clicking each process in Windows Task manager, selecting Set affinity... and unticking one or two of the Cores? Should this have been done before starting rendering or can it be done now with no major ill effects?

[#2]

I couldn't comment with any authority upon setting affinity (I have only altered that for a game during the game running - and it was fine, but I'd guess it could have caused a problem ???). I would simply reduce priority. I know that at least when I encode video the second pass always uses pretty much all of my CPU power if I leave it on 'normal'.
Anyway, DivX? There are really people who are still using that codec?  You'd do far better with a .h264 codec like x264 (via MeGUI, for example). Then again, would depend if your devices support it.

[#3]

The main issue was that I was running both Handbrake and DivX Plus Converter together. Fine while I was asleep but problematic once I wanted to use the PC again. D P Converter was set to Below normal priority but Handbrake was set to Normal.
DivX Plus Convertor does convert to H.264/MPEG-4 depending on what setting you use and I have some files that don't render so well, if at all, with anything else. As these files will never ever get edited I am happy to go with what produces the lowest file size while keeping the quality.
I do have dedicated software but that would be overkill in this instance. Both Handbrake and DivX Plus Converter produce excellent results. DPC is currently reducing a 27GB 1920x1080 file to under 6GB.

[#4]

I normally just chuck any video encoding jobs over to my server and let them run on whatever spare capacity the cores have.

[#5]

Quote from: Mav

DPC is currently reducing a 27GB 1920x1080 file to under 6GB.

That would be within the range of what I'd expect with some of my encodings that I know I can save space on, others definitely not. Either way if you've got a method that works for you, that's all that really matters. At least you are using the more efficient h264.
As to priority, I know what you mean about it being ok when you can let it run overnight. I try to set up as much as possible that way, but it doesn't always work out like that. With some projects I need to be editing both video and audio (usually the full six channels) at the same time as encoding something else (both video and other audio) because I've had so much to get through. When it's like this I'm working constantly over four HDDs so as to impede processes on each drive as little as possible (not clash them in terms of which disks are being used at which moments), and I set the x264 encodings to below normal most of the time, sometimes briefly to low when I need to extract anything from a file. This way I find I can be running several things at the same time, all with the view to setting up for the overnight video encodes so that come that completion all the audio is ready and whilst they mux I can be setting up the next batch to work on. Either way, the whole thing has driven me insane. I am glad I am at the end of a project that has taken me some months to complete. I hope it's not so long for you with whatever you're encoding, and it all works out smoothly.

[#6]

Not sure how long it took to reduce the file to under 6GB but it had completed by the time I got up
Happy with the result as it was almost impossible to see any difference between the two files. Have deleted the original now but I have quite a few more to do.
Sometimes I truly forget to lower the priority and, like you, can have several things going on at once from encoding to editing to copying. Even with temporary files on an SSD, 6 cores and several external hard drives each dedicated to one tasks things can slow to a crawl. Occasionally I'm happy to let that happen and work on my OU course using the laptop (all course work is save to the cloud anyway) meaning I can leave the PC to do its job.
Yesterday I noticed all 6 cores were working at 100% yet the core temps stayed below 60C. Trouble is I've been so busy with many different projects, sorting out my mother's finances and study that I still haven't fully edited my last trip to see SWMBO's family two years ago!

[#7]

Quote from: Mav

DPC is currently reducing a 27GB 1920x1080 file to under 6GB.

27GB for a video? 

[#8]

Bluray rips can exceed this .....

[#9]

I record at 1080p 50fps with a bitrate of around 25Mbps which can result in some huge file sizes.
SWMBO likes to keep a copy the unedited footage so I whittle it down as small as I can get without compromising quality.
Personally I like to whittle down 2/3 hours of footage to 20/30 minutes of watchable stuff