Your system supports RAM speed up to 2133 MHz, according to Dell's specifications. You may be able to use faster RAM, like some of those that Crucial guarantees compatible with your system, but it will downclock (run more slowly) to the maximum speed that the system supports, which is 2133 MHz. Other brands may work as well. I listed Crucial because they guarantee that RAM to be compatible. Whenever touching components or working inside a computer, wear a grounded wrist strap, also called anti-static wrist strap, ESD wrist strap, or ground bracelet. It's a cheap and sensible precaution. Rest the laptop on an anti-static mat or at least a reasonable alternative such as corrugated cardboard. (Repeatedly touching a metal case part is not sufficient mitigation with modern components.)
I'm thinking of buying a Precision T36200 that does not have ram. I was really surprised at the price on eBay for 2133 ram for this system? I would think I could use other NECC ram like DDR4-2400 or 3200 that would run at 2133. Has anyone had experience with this and how did it work for you? John
Precision T3620, memory DDR4-2133 vs 2400 or 3200?