From the Hiawatha 8.1 blog entry comment:
[...] the i686 [build] requires a Pentium 3 or newer CPU. If your processor supports the i686 build however, my quick & dirty benchmarks show a roughly 7% improvement in serving static content, and around a 25% improvement in PHP rendering time via FastCGI.
My Linode 1024:
$ cat /proc/cpuinfo | grep name
model name : Intel(R) Xeon(R) CPU L5520 @ 2.27GHz
model name : Intel(R) Xeon(R) CPU L5520 @ 2.27GHz
model name : Intel(R) Xeon(R) CPU L5520 @ 2.27GHz
model name : Intel(R) Xeon(R) CPU L5520 @ 2.27GHz
I've tried looking up information on Intel processors at Wikipedia, but am not sure if I should use the i686 build or not.