gcc and alphalinux

Tenhave, Tim Tim.Tenhave at compaq.com
Thu May 25 09:35:03 PDT 2000

Hi Matt,
*  Have you asked your questions to the peer-to-peer Compaq compiler support
program that is maintained by the folks from the University of New
*  Here are some random thoughts from another engineer more familiar than I
on the EV5/56 compiler issues...
Differences in performance between Linux and Tru64 can be caused by

several reasons:

(1) gcc vs. ccc. This person has eliminated this difference by using

ccc on Linux.

(2) Compile switches. I recommend starting with "-O -fast" although

floating point intensive C programs might also like -O4.

(3) Prefetching. The compilers on Linux do not do this because of a

bug in the Linux MILO PALcode for EV-5 and EV-56 systems. If the

customer had an EV-6 based Linux cluster then using "-arch ev6" will

turn on prefetching because the Linux PALcode bug does not occur on

EV--6 system.

(4) Page coloring. The Tru64 kernel does this and Linux does not.

(5) Speculation. The Tru64 kernel supports this and Linux does not.


Hope this helps...





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