On Sun, Aug 21, 2011 at 19:42, Thomas Schilling wrote:

On 16 August 2011 15:39, Johan Tibell wrote:

...

the CPU masks out the last 5 bits in the shift amount and only uses those when shifting

As an aside, this may be how it's specified now in all modern x86(-64) CPUs, but it definitely wasn't true for all CPUs. Some older x86 CPUs actually would set the value to zero if the shift amount was greater than the word length. (I'm not sure which, but may have been different in early 386 CPUs and Athlon CPUs.)

FWIW I vaguely recall a bit of an outcry when this changed on Intel CPUs. It may have been around the 80486. -- brandon s allbery allbery.b@gmail.com wandering unix systems administrator (available) (412) 475-9364 vm/sms