Re: New SYSCALL instruction (was: Re: Call Gates)

Linus Torvalds (
21 Jun 1997 03:25:08 GMT

In article <>,
Alan Cox <> wrote:
>> All newer pentiums & pro's, and the K5 and K6 have the newer SYSCALL/SYSRET
>> instructions: 2 byte opcode, and upon entry to the system only cs and the stack
>> are reloaded. This is very fast :-) Anyone looking into implementing this as
>> an alternative to int $80 in the linux kernel? A lot of syscalls can do without
>> to much protection :-)
>> btw, this instructions are described in detail in the K6 databook...
>Interesting to note they dont appear in the Intel PPro databook. So either
>its an AMD special or Intel are pulling appendix-H type games again

Intel is pulling Appendix-H again - look at their web-site.

Also, it should be pointed out that the AMD and intel versions are
likely to be wildly different.

At this point in time it doesn't make much sense to use the feature, but
we'll see - eventually it might make a difference.