Reading Hennesy's book "Computer Organization and Design" it is mentioned "Register.Rd" and "Register.Rs" but what does it mean? The .Rd, .Rt and .Rs parts I can't understand, on page 365:

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They are just generic ways of referring to cpu registers:

  • Rd is usually denotes a destination register.
  • Rs, Rt usually denote source registers.

For example, a cpu instruction could be:

add Rs,Rt,Rd

Which would mean: Rd = Rs+Rt

The Rd,Rs,Rt are placeholders for the actual registers used in this instruction. A specific example for this instruction could be:

add $1,$2,$3

Which would mean "write the sum of specific cpu registers $1 and $2 into $3".


I'm not very familiar with this exact subject, but within instruction sets tables for microcontrollers these conventions are often used:

  • rd : destination register
  • rs : first source register
  • rt : second source register

This looks quite similar with your quote.


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