Address Error Exception
On the Nintendo 64's CPU, the VR4300 can throw an Address Error Exception. This occurs when lookup to an invalid or non-existent address occurs, most commonly as a null-reference exception.
Exploits
Because the exception only occurs on the N64 and not the Wii VC it could potentially be exploited. The Wii VC will skip the write or read when the exception would occur. This means that a read from an invalid address into a register will actually leave the register untouched with its last value and resume normal execution.
We can then analyze crashes that cause Address Error Exceptions.
| Cause | ACE Exploitable | Any Exploitable | Notes |
|---|---|---|---|
| Exceed the object limit | |||
| Have too many objects at once on the screen | |||
| Walking at PU speed for only a portion of the 4 quarter steps on a frame | |||
| Moving at PU speed with no joystick input for all 4 quarter steps on a frame | |||
| Moving at PU speed directly into a wall | |||
| Deleting a non-existent file on the File Select Screen | |||
| Moving a shadow above surface 12 while it's over OOB | |||
| Killing a Monty Mole remotely | |||
| Killing an uninitialized Monty Mole | No | No | |
| Going out of bounds in a room with a painting | No | Maybe? | `D_8035FF90` is set to t4 |
| Being pushed off of a hang-able ceiling while in the idle hanging action | No | Doubtful | t9 for start hang. Would potentially cause Mario to stay hanging for a single frame without a ceiling, No effect for t8, last use of t8 set is jr t8 which is not the hang-able value 0x05) |
| Sound glitch | Since sound glitch only exists on the original Japanese N64 version, which wasn't released in Wii VC, this cannot be used or exploited in Wii VC legitimately | ||
| Moving the camera immediately when entering VCutM |