 Basic TLB operation

Ciro Santilli 34  Updated 2024-12-15  +Created 1970-01-01

After a translation between linear and physical address happens, it is stored on the TLB. For example, a 4 entry TLB starts in the following state:

  valid  linear  physical
  -----  ------  --------
> 0      00000   00000
  0      00000   00000
  0      00000   00000
  0      00000   00000

The > indicates the current entry to be replaced.

And after a page linear address 00003 is translated to a physical address 00005, the TLB becomes:

  valid  linear  physical
  -----  ------  --------
  1      00003   00005
> 0      00000   00000
  0      00000   00000
  0      00000   00000

and after a second translation of 00007 to 00009 it becomes:

  valid  linear  physical
  -----  ------  --------
  1      00003   00005
  1      00007   00009
> 0      00000   00000
  0      00000   00000

Now if 00003 needs to be translated again, hardware first looks up the TLB and finds out its address with a single RAM access 00003 --> 00005.

Of course, 00000 is not on the TLB since no valid entry contains 00000 as a key.