You may have said it yourself.
When running 15 clients you are maxing out your VRAM, so if you add more clients, then performance will drop dramatically as the VRAM does not have enough room to deal with them, and resorts to swapping in and out of system RAM, which might also end up paging (although probably not seeing as you have a fair bit free).

Your CPU is fairly high with 15 clients, and adding more game clients and then frame swapping to the list, you might be nearing the maximum effective there too. CPU's are a bit weird in that once you start to get over 90% sustained utilization across the board, they start to become inefficient and less likely to respond well to spikes.

With CPU limits you get hit with a double whammy. 1. the scheduler starts chewing more kernel time ordering and querying processes to see if they need a time slice (effectively the number of context switches increases disproportionately to the number of processes added) 2. you have more processes that want to use their time slice because it is not coming up as often.


When you say "anything lower than 1600x900 I get this throttling symptom", this means you've tried lower resolutions? It would be weird that lowering the resolution causes a problem on a working setup, but if you are adding more clients at the same time, then it may be a CPU limit rather than a video limit.

For the graphics you could go down to 1280x720. This keeps the aspect ratio, while lowering the number of pixels per client by around 33%. This won't help if your problem is the CPU though, but it could alleviate some pressure if that is coming from frame swapping.

1600x900 = 1440000 pixels
1280x720 = 921600 pixels.