OK, I'm confused (nothing new there)- my Linux server is an AMD K6 that has crap parts in it and I'm having issues with the CPU. Well, not really the CPU itself, but what it can do- I've compiled and run some i686 apps just fine and run into no problems, but other i686 apps give errors that either imply that it can't be run since I don't have an i686 CPU or they flat out tell me to go down and grab an i586, i386, etc version. (I had to find an i386 SETI@home to get it to work on there.)
Googling gives me conflicting answers on wether the K6 is an i686 or an i586 with some i686 extentions. I thought it was a i686 like the Pentium 2 was, but maybe it's only partly an i686. I dunno. If anyone can shed some light on the matter, please do.
Also, this link I found http://www.rebourne.org/chiparch.htm says it's roughly equilent to a Pentium Pro, but also lists as a i686. He also said the Duron isn't a full K7, the K6-3 is a K5, etc so I bet he's as lost as I am.
Hence, the reason I always stuck with Intell ...
Well, I was always told that the K6 was the same as the the pII speedwise. However, the instruction set was not as complete as the pII. There were differences in the AMD Now thing and Intel's MMX. Also, the instruction set of the K6 was not as complete as the pII. So, if you are using an app that is using one of the oddball instructions that the pII has, but the K6 does not, then you do need to downgrade the optimazation of the code.
That's just the way it was explained by my brother ... er ... well, my interpratation of it. He works at Intel, the other reason why I buy Intel. I must say that AMD CPUs before the Athalon series were just not up to spec with the Intel counterparts.
I hope this helps. Unless somebody wants to correct a bit of what I said here.
Jon
The AMD K6 is an i586-class CPU. Likewise, the 6x86 is a 586, and the 5x86 is a 486.
Don't get too worried about getting open source code that has been built specifically for a certain CPU type. GNU/gcc's optimization code doesn't give you much benefit.
Therefore, an i386 application probably won't perform noticeable slower for you than an i586 application.