We've just updated MediaWiki and its underlying software. If anything doesn't look or work quite right, please mention it to us. --RanAS
Y Index Register
From SnesLab
The Y 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.