Ys Japan Glitch

[mathieulh]

On the Japanese FM enabled version of Ys, there is a graphical glitch visible as soon as you staty the game, this glitch does not occur on the US version of the game.

[theflynn49]

Hello
Quand on fait tourner cette version avec Emulicious, on a exactement le même problème, ce qui laisse à penser que ce problème est dans la ROM et non pas dans le core ...

[ekeeke]

That game relies on some undocumented VDP feature (only existing in earlier 315-5124 VDP model), see https://www.smspower.org/Development/TilemapMirroring

[theflynn49]

Nice catch ekeeke ! We may have to add a "VDP Version" parameter, which is a shame for only one game, but hey ...

[theflynn49]

I just gave it a try with this "vdp-v1" patch

( vdp_v1.txt ) (patch removed, it was too wrong to survive)

but it failed miserably (no effect whatsoever). I need to put more thought into this.

[sorgelig]

Why simply don't use US release? This is the only game affected and only Japanese release. And as far as i understand it's not a bug, but just different revision, so basically nothing to fix.

[theflynn49]

@sorgelig.
Yes of course.

On another hand, don't we want a perfect hardware emulation of all versions of these consoles ? Isn't that the very reason for MiSter to exist ?
I have the patch to make it a SMS version 1 VDP :
vdp_v1_2.txt

The only bad thing about it is the need to add a "vdp version" parameter to control this modification, to achieve basically something that is only a pedantic kind of feature to please the hackers and confuse the end-user ... Nevertheless, I'd be so deceived to let this core exist with an imperfection ...

Tell me how you want this to be done, your decision prevails.

Edit: after thinking about it, I propose to add a commented modification in the source of vdp_backgound.vhd so if someone wants to play Ys Japan, he can recompile the core after re-enabling the commented lines ...

[sorgelig]

It can be auto-enabled when this game is loaded (by checking game ID in the ROM).
But since US version works without this glitch i don't want to spend my time for this. Is US version different?

[theflynn49]

No idea, maybe @mathieulh can tell us why he desperatly wants to play this version.

There is a Rom ID somewhere ? Where is it ? is this a reliable ID with guaranteed no-collision ?

[sorgelig]

There is a Rom ID somewhere ? Where is it ? is this a reliable ID with guaranteed no-collision ?

it's generic concept, i didn't look into SMS ROM format. If there is no ID, then simply can calculate the checksum of whole ROM or part of it while loading.

[theflynn49]

Ok, I think I've seen a thread discussing a checksum mechanism a while ago, must be it.

So I propose :

• adding a comment with the modification in vdp_backgound.vhd so if a hacker wants to enable the VDP version 1 for fun, he will find how to recompile the core to do it
• if the Japanese game does not differ from the US one, let it stay like this.

[sorgelig]

that's fine to me

[theflynn49]

@mathieulh : you can test the model1 SMS core here =>
https://github.com/theflynn49/MiSTer_cores/raw/master/SMSVDP1_20200205.rbf
warning : I do not guarantee anything with this core, since I compiled it with Quartus16, but it works with me.
Please tell us if the Japanese version of Ys is different from the US one.

[mathieulh]

@theflynn49 your fix works, I tested it successfully on the Japanese rom

[mario-64]

Japanese version is FM enabled while the US version is not. That’s one difference

[thehughhefner]

Has this issue been fixed? YS jap version has FM audio while the US version does not have FM audio.

[birdybro]

#132 - This resolves the issue. Here's the RBF for you to preview if you want.

SMS.zip

2022-07-07.21-38-46.mp4