I have a Workstation T5500 with some upgrades already into it. It has two Intel Xeon X5675 processors on a Dell 0WFFGC A00 motherboard with 64 gb of mem. It's not fast enough for day trading. I would like to know if I can upgrade it replacing the X5675 processor for an AMD Ryzen 9 5900X using the same motherboard? If not, which motherboard should replace it with? Do I need to replace anything else? Thanks in advance!!
First the processor you posted is a Intel Xenon processor so you would need to replace your motherboard with a AMD Socket motherboard.
If you are planning on using the AMD Ryzen 9 5900x processor you need to go the Motherboard's QVL List for RAM MEMORY for the 5000 Series processor to see which RAM modules are compatible with both the Motherboard and Processor. In case your current RAM doesn't work with the AMD processor.
You also going to need to purchase a high quality CPU Cooler, preferable a AIO Liquid CPU Cooler to keep your Ryzen cool.
At PCPARTPICKER.com it shows all the compatible Motherboards for the Ryzen 9 5900X: https://pcpartpicker.com/products/motherboard/?compatible_with=KwLwrH
Also you can see all the compatible CPU Coolers and Memory.
But since you are using a Business type computer maybe you might be interested on the AMD Threadripper processors. They are more expensive but are more powerful then most AMD processors.
As an example only here is AMD latest powerful Threadripper: https://www.amd.com/en/products/cpu/amd-ryzen-threadripper-3990x
Here are all the compatible Motherboards for the Threadripper 3990x: https://pcpartpicker.com/products/motherboard/?compatible_with=KWmFf7
But if you have a budget and can't spend around $4000 to $6000 dollars for a processor and several hundred dollars for a motherboard then the AMD 5000 series would be a good choice.