Building notes, projects, and occasional rants

Tip: does my CPU support EM64T extensions?

This was a question I was wondering for quite some time. All the things I read about this pointed to a positive answer: I have a Xeon CPU and all Xeon CPUs since second quarter 2004 support EM64T.

But I wanted something more reliable, like a cat /proc/cpuinfo flag. And I finally found a post that gave my some hints about detecting EMT64 from the cpuinfo flags. It describes the lm flag as "long mode", having the 64bit extensions, but it talks of those in AMD context.

Further googling turned up this Debian mailing list post and a MySQL commit message, and they seem to confirm this: even on Intel CPUs, lm CPU flag means 64bit extensions.

Now the question for all: if I have a dual Xeon processor, is it worth it running CentOS with EM64T extensions or should I just run normal i386 version?