On Mon, 10 May 1999, Pavel Machek wrote:
> 
> It seems to me that with new kernels rdtsc is not being used unless
> cpu type is set to 586/TSC+. This is difference from old kernels which
> used rdtsc whenever it was available. This is why my badboy exploit
> stopped running on my home computer.

No, new Linux kernels will use rdtsc in all situations that older kernels
used to as well. 

HOWEVER, there are a set of circumstances where an old kernel would
_never_ have used rdtsc, and a new kernel will. Most of those are so
performance-critical that some people (namely me and Ingo) felt that the
only way to support it was to just require it at compile time. 

So think of the compile-time option as giving up an extra choice that
wasn't available before.

		Linus


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