64K Bank-Boundary Walk
Signals & AudioTwo far-pointer walkers approach the same gold seam from opposite directions while indexed reads independently verify every byte.
Self-running — verified CRC 4ED7.
Click the screen, then play. (Tab away and it pauses.)
The seam under test
A generated HiROM table begins at C1:0000. The probe starts at offset FFF0 and reads 64 bytes across C1:FFFF into C2:0000 three ways: *p++, runtime indexed offsets, and *p-- in reverse. The data formula includes the bank ordinal so a lost carry cannot alias the expected value.
Shape: non-LTO disassembly contains lda [dp] far loads and verified 24-bit pointer arithmetic.
Result: host, a16, and xy16 all return 0x4ED7 on MAME and bsnes-jg.
What it shows
Blue and magenta trails are the forward and reverse sample bits. Their cursors cross the gold vertical bank seam in opposite directions; a bad bank-byte carry breaks the trail immediately.
Compiler stress-test #128, Round 7.