YRW-801 analysis

By Eugeny_Brychkov

Paragon (1173)

Аватар пользователя Eugeny_Brychkov

09-02-2021, 16:34

I am analysing the contents of the OPL4 ROM, and it seems I am missing something. There're instruments overlapping each other (316 to 330 overlap other instruments), and I calculated 626 kB of unused space (out of 2 MB), not related to any instrument with proper layout. At the same time these unused locations contain some non-uniform bytes. Invalid instrument 330 refers to the wave data with "YAMAHA.YMH" in it, which must not be valid wave data.

Anyone have done this ROM analysis before? Findings?

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By Eugeny_Brychkov

Paragon (1173)

Аватар пользователя Eugeny_Brychkov

10-02-2021, 11:13

I have made mistake in calculating the allocation of samples. After correction ROM is having just 229 bytes of unused space.

By Grauw

Ascended (9899)

Аватар пользователя Grauw

10-02-2021, 11:16

Good, that makes more sense!

By sdsnatcher73

Paragon (1972)

Аватар пользователя sdsnatcher73

11-02-2021, 13:41

So what are your goals for this analysis? I am genuinely curious. Any other findings so far other than the unused space in the ROM?

By Eugeny_Brychkov

Paragon (1173)

Аватар пользователя Eugeny_Brychkov

11-02-2021, 15:08

I needed 24 bytes at the end of the ROM. It appeared that there're only 4 unused bytes at the end, and they are also not actually unused, but identifiers of the ROM version. And second task was to validate the contents and ensure I understand the layout.