H. Peter Anvin (
6 Aug 1997 01:16:59 GMT

Followup to: <>
By author: Ingo Molnar <>
In newsgroup:
> does anyone know how much latency the SYSTENTER/SYSEXIT instructions have?
> (opcode 0f 05 and 0f 07). Are they better than the 85 cycles int $80 +
> iret pair?

It would be extremely useful to have more detail of the relationship
between the Intel SYSENTER and the AMD SYSCALL instructions; however,
from the description of the latter I suspect that they are extremely
fast, but can only be used in a very specific set of circumstances,
which, however, Linux 2.1.x may either satisfy or can be fixed to

Anyone who either have or can obtain (through experimentation or what
have you) information about these instructions it would be incrediby


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