default x2apic cluster mode on platforms
supporting x2apic.
+ x86_mrst_timer= [X86-32,APBT]
+ Choose timer option for x86 Moorestown MID platform.
+ Two valid options are apbt timer only and lapic timer
+ plus one apbt timer for broadcast timer.
+ x86_mrst_timer=apbt_only | lapic_and_apbt
+
xd= [HW,XT] Original XT pre-IDE (RLL encoded) disks.
xd_geo= See header of drivers/block/xd.c.