This hack fixes a bug (really an oversight) that affects Tunnel Rhino and allows him to use his drill projectiles 100% of the time. Usually if you reach his boss room without dying, he won't be able to use his drill projectiles. Losing a life while fighting him and re-challenging him "fixes" this.
This patch rewrites a function, called when a boss door is opened, to fully clear the enemy/object stack/table. The code usually in this function only clears a few bytes (in each entry of the table) and one of the bytes not cleared keeps track of Rhino's drills, hence the bug.
This has been tested on real hardware with no noticeable performance detriment and I've play tested it from start to finish with no game breaking bugs noticed.
The IPS file can also be used with Rockman X3 (CRC32:E476912B/SHA-1: 8E0156FC7D6AF6F36B08A5E399C0284C6C5D81B8) since the function resides in the same location.
Database match: Mega Man X3 (USA)
Database: No-Intro: Super Nintendo Entertainment System (v. 20210222-050638)
File/ROM SHA-1: B226F7EC59283B05C1E276E2F433893F45027CAC
File/ROM CRC32: FA0FE671