From Mandriva Community Wiki

[edit] VIA C3 and EPIA Processors

• These processors are 100% i586 capable but some models are not i686.
• Usually integrated onto small form factor mainboards and some ultra quiet or ultra cheap PCs.
• Some VIA CPUs with Ezra-T, Esther or Samuel cores do not understand the SSE2 instruction set (NOT i686).
• Later processors based on the Nehemiah core do not have this problem.
• Generally, if you have a VIA CPU then choose an i586 package over an i686 package. -- Main.MatthewPROUSE - 01 Dec 2004

[edit] Intel Pentium4

• Pentium 4 processors with the hyper-threading (ht) feature require an SMP (multi-processor) kernel if HT is enabled.
• My ASUS P4C800E Deluxe was too unstable to use with ht enabled until I installed the SMP kernel - JoeDullemond
• Due to a security issue in the kernel, until now (12 Jan 2006) it is advisable to boot with lilo append parameter "ht=off".