We've just updated MediaWiki and its underlying software. If anything doesn't look or work quite right, please mention it to us. --RanAS
X Index Register
From SnesLab
The X Index Register exists on 65x processors and often holds the current index when iterating over things.
On the S-SMP it is always 8 bits wide. On the 65c816, it may be 8 or 16 bits wide.
Unlike the Y index register, the value of the stack pointer can be transferred to/from X. See TXS and TSX.