bad use settings causing malfunction???

[||kafre||]

i know this sounds weird but recently installing gentoo 2004.1 in one of my computers i used -march=athlon-xp but i forgot the processor was a thunderbird. It finished compiling everything but a few apps didnt work. Texinfo, procps .... the question is, athlon-xp and athlon-thunderbird are similar proccesors, how much can affect using bad use settings to the stability and proper function of packages or entire system? i mean a xp processor has more instructions than a thunderbird one but doenst it keep any compatibility in use flags enough to make packages work?

[NeddySeagoon]

||kafre||,

Packages that compiler produces using the new instructions will break with an illegal instruction exception when the first such instruction is encountered. It will vary from application to application and the effects will be from never happens, some things don't work, app won't even start.

There are two similar CFLAGS -march and -mcpu, one preserves compatibility back to the 386, just reordering instructions for maximum speed. The other breaks compatibility for best possible performace. See man gcc for details.
_________________
Regards,

NeddySeagoon

Computer users fall into two groups:-
those that do backups
those that have never had a hard drive fail.

[||kafre||]

thank u, i understand the difference between -march -mcpu, in fact i´ve been using gentoo for more than one year, but this was the first time i made it so bad. Illegal instruction was the error i had with the packages not working. Thanks por explanations.