V9990 bug related to R#22

[albs-br]

Hi guys, me and some fellows on MSX.org found a bug on the V9990 implementation, more specifically on R#22:

The two higher bits (bits 7 and 6) are supposed to disable layers AND sprites, not just the tile patterns layer.

The documentation states:
SDA: Set to "1" to disable layer "A" and sprites.
SDB: Set to "1" to disable layer "B" and sprites.

The discussion can be viewd here (page 4 onwards).

If necessary I can provide a test ROM showing the bug.

[ppeccin]

Hello... Wow, that's odd. Thanks for reporting! You mean then that it is impossible to disable only the pattern layers A and/or B and leave the sprites active? Paulo

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On Wed, Nov 30, 2022 at 7:18 PM André Baptista ***@***.***> wrote: Hi guys, me and some fellows on MSX.org found a bug on the V9990 implementation, more specifically on R#22: The two higher bits (bits 7 and 6) are supposed to disable layers AND sprites, not just the tile patterns layer. The documentation <http://msxbanzai.tni.nl/v9990/manual.html>states: SDA: Set to "1" to disable layer "A" and sprites. SDB: Set to "1" to disable layer "B" and sprites. The discussion can be viewd here <https://www.msx.org/forum/msx-talk/development/samurai-shodown-unplayble-demo-on-msxv9990?page=3> (page 4 onwards). If necessary I can provide a test ROM showing the bug. — Reply to this email directly, view it on GitHub <#90>, or unsubscribe <https://github.com/notifications/unsubscribe-auth/AAFOLIE37YPW6RFWCMB54GTWK7HCXANCNFSM6AAAAAASQDWNPY> . You are receiving this because you are subscribed to this thread.Message ID: ***@***.***>

[albs-br]

I made some ROMs to help openMSX folks to fix this same issue on openMSX: openMSX/openMSX#1466

Maybe it helps here too.

[NullPointerReference]

@albs-br I think this is an easy fix in the WebMSX code; and I downloaded all 4 example ROMs, but it's not fully clear to me what the expected 'output' on screen is (don't have a real V9990 either); given the MSX.org thread linked from the OpenMSX ticket doesn't have any pictures (anymore ?) for me to check and it you also mentioned that variant D looks different on real hardware from what you described originally / above ? And it also isn't fixed in OpenMSX 20 either.

1. So what is the exact 'correct' output for ROMS B and C and D ?
2. As you can see currently in WebMSX, ROM variant D still shows some 'green tile/block/sprite';
   is that expect or a / another bug too ?