Hi! I wasnt sure which thread to post in since this could end up being related to multiple (CPU upgrade, NVIDIA in older Mac Pros, Mavericks on older Mac Pros), so instead I decided to create a new one. Im in the process of upgrading my aging Mac Pro 1.1. So far, I have: - Upgraded the firmware from 1.1 to 2.1 - Installed Mavericks 10.9.1 - Installed an EVGA GTX 660 Other than that, I have 8 GB or RAM (more on the way though) and the original 2 x 2.66 GHz Dual Core Xeon. Everything is running smoothly, except my gaming performances. Im mainly using Borderlands 2 and Starcraft 2: Heart of the Swarm as my guides. When in Borderlands, I often get stutter at average settings. I tried lowering them, and while thing would get better, I could always sense that things wouldnt go smoothly in certain area. I ended up with super low settings and the game would still slow down when moving around looking at specific places. I opened activity monitor to see if something was wrong, and I noticed that the CPU use for Borderlands is 120%, no matter what I do. Since I feel like I pretty much took the graphic card out of the equation by lowering the settings to the absolute minimum, Im wondering if the CPU is the bottleneck. I am very surprised that, even though theyre old processors, Borderlands 2 wouldnt play on Quad Core 2.66 GHz Xeons at the lowest settings Any idea what could be done? To either test out and isolate the problem, or fix it. I have replacement processors coming (changing the 5130 for 5355), but since they have the same clock speed I dont expect any improvement Thanks!