Question T5500 Workstation: Can I use these CPUs together?

Jun 23, 2021
I have owned a Dell T5500 workstation with a single Intel Xeon 5650 CPU for years now. I've upgraded it in many ways over the years and I've been so happy with this machine that I don't want to kiss it goodbye, but I'm finally hitting the limits of its hardware capabilities in both my professional work in financial simulation and hobby work in game theory optimal poker.

I am upgrading the CPU to the 5690 in a few days (new CPU on its way) and I'm going to have the old 5650 CPU to do something with. Given the T5500's support for dual Xeon processors, I was wondering if I might be able to purchase the correct riser/heat sink assembly and use the 5650 at the same time. Can I use two different CPUs like that, 5650 + 5690 together in a T5500?

I am sorry if this is an idiotic question, but I'm a real hardware noob. Thanks for any help you can offer.
Generally, and almost universally, dual cpu systems need identical cpus to boot and function properly.

However, that being said, if you have the processor spare, I would try it because the hp z600 (t5500 competitor) actually can use two different processors. I wouldn't have believed it except someone posted screenshots to confirm it. The T5500 may have a similar capability that has just never been tried.