The later 'um80xx' versions are a superset of the 1977 manual, and, in particular, the 2004 version PDF version directly from Zilog (when scaled to "fit page")

The later 'um80xx' versions are a superset of the 1977 manual, and, in particular, the 2004 version PDF version directly from Zilog (when scaled to "fit page") has much more readable fonts (for me at least) and is super-fast to page through. Very good when not using a hard copy. Great index too. The bitsaver scan of the 1977 version is almost painful to use in comparison: More difficult to read, no index, slow.