[RC5] keyrate stabilizing?

Dan Sugalski dan at sidhe.org
Fri Oct 19 17:51:44 EDT 2001

At 02:32 PM 10/19/2001 -0400, waldo kitty wrote:

>i don't agree about rotate and others being useful _only_ in
>encryption... consider a program that uses bits to represent command
>line parameters internally... i have used this myself... don't know how
>to explain it without giving info that's under NDA other than to say
>that each parameter is represented and then "stepped thru" via the
>rotate due to the numerical values that result from each rotate... call
>it a validation methodology...

While rotates are useful in this case, and a few other isolated places, 
this is such an edge case that it's just not worth the silicon that it'd 
take to implement a rotate instruction. Not having one simplifies the ALU a 
bunch, and that speeds up the core and leaves more room for other things. 
Even if a CPU fakes it, like the newest intel and AMD chips likely do, you 
still get a win. (Heck, if all tossing rotate out got you was another line 
in your L1 cache it'd be worth it...)


--------------------------------------"it's like this"-------------------
Dan Sugalski                          even samurai
dan at sidhe.org                         have teddy bears and even
                                      teddy bears get drunk

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