When choosing, you always need to consider whether your processor will fit the motherboard you are using. You should understand that each processor has its own socket (programming interface) and if your processor has a socket, for example, AM3+, then it will not work on an AM3 socket.
From personal experience, I bought an 8-core processor, but did not check whether it fits my motherboard, which is why I had to spend additional funds on a new motherboard.
of the processor with the motherboard and with the amount of RAM.
Heat transfer
Each processor heats up during its special lead operation. So that it does not fail, it needs cooling and that is why it is worth paying attention to this item. For example, you bought a new processor for your server, but did not pay attention to the heat dissipation and used the cooling system as on the old processor - this can lead to unstable operation of the new processor or its complete failure due to constant high temperature. To avoid this, always check the amount of heat generated by the server and use a suitable cooling system.
Frequency
Frequency is the data processing speed on the processor (measured in Hertz), as a rule, the higher the GHz, the faster the processor can execute the commands assigned to it. However, this is not the main indicator of processor speed, because in some cases processors with lower frequency indicators work faster, this is all due to the processor architecture.
GPU
A graphics processor that may be present in the processor. It helps the system to process graphics-related data more quickly, for example, if you use a large amount of graphics (3d or otherwise) in your work, then this type of processor will be very useful. With the simultaneous presence of this processor and video card, the system will not be loaded when processing graphics processes.