I am studying Intel Protected Mode. I found that Call Gate, Interrupt Gate, Trap Gate are almost the same. In fact, besides that Call Gate has the fields for parameter counter, and that these 3 gates have different type fields, they are identical in all other fields.
As to their functions, they are all used to transfer code control into some procedure within some code segment.
I am wondering, since these 3 gates all contain the information needed for the call across privilege boundaries. Why do we need 3 kinds of them? Isn't 1 just good enough?
Thanks for your time and response.
Update 1
A related question: When to use Interrupt Gate or Trap Gate?
Update 2
Today I came up with this thought:
Different purpose, different gates, and with different CPU behavior details carried out. Such as IF flag handling.