athlon xp vs. athlon mp (ot...kinda)

[christopher j bottaro <cjb cs utexas edu>]

hello,
sorry this is kinda off topic, but this mailing list has tons of smart people 
who's opinions i can benefit from.

i decided that i want a dual cpu system.  i'm kinda interested in 
parallel/distributed programming.  my friends have donated their old 
computers and i now have a 5 node linux cluster (just old cheap 500 mhz 
p3's).  thats fun to play around with for distributed stuffs, but now i want 
a dual cpu system to play around with shared memory parallel programming.

so now down to the question.  whats the difference between a dual athlon xp 
system and a dual athlon mp system besides a >huge< price difference?  the 
dual mp motherboards are twice as expensive...as are the athlon mp 
processors.

again, i'm not doing any major server stuff that requires top of the line 
performance.  i just want something to play around with (that will be stable 
of course)...and maybe something i can encode a divx on while at the same 
time compiling kde...;)

also, how supported is this kinda stuff in the linux kernel in redhat 8.0?  
does xp vs. mp make a difference to the linux kernel?

thanks for the info,
-- christopher