Recently I've been writing a bot for a game which renders using DirectX. When I run multiple instances of the game, it takes a toll on my computer's CPU/RAM usage. Can I stop DirectX from rendering to increase performance? If so, how?
If you stop D3D from rendering -- typically by detouring the D3D calls directly -- you may see an increase in performance. It will depend primarily on whether the application's performance is actually bound by limitations on the GPUs resources.
You may also destabilize the game, which may be making some decisions based on responses it gets from the GPU (for example by using queries) which it will of course no longer get, since you suppressed transmission of any commands to the device. Ideally of course, rendering and game logic are wholly separate, but sometimes this isn't the case.
You'll probably have to do a fair bit of juggling and balancing what you detour. You could, for example, allow all resource creation to succeed so that you don't have to deal with the game not coping with your proxy resources (which may not match its internal validation), but if the problem you're seeing with performance is that you're overloading the resources stored on the GPU, you will not see any benefit from this approach.