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dmitry-shechtman
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Close #625

@ISSOtm
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ISSOtm commented Oct 4, 2025

Wait, really? I thought only another MASK_EN command could unfreeze the screen.

@dmitry-shechtman
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Maybe it needs clarification. If the screen was frozen by clearing LCDC, it will be unfrozen when its bit 7 is set.

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ISSOtm commented Oct 4, 2025

Ah, I see: it's another freezing mechanism, separate from MASK_EN, right?

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Yes. Enlightened by beware.

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Then I'd like to suggest the following wording:

Comment on lines +29 to +30
SGB freezes/unfreezes the Game Boy screen automatically whenever the LCD is
turned off/on.
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@ISSOtm ISSOtm Oct 4, 2025

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Suggested change
SGB freezes/unfreezes the Game Boy screen automatically whenever the LCD is
turned off/on.
The screen retains its last frame when the "LCD" is [turned off](<#LCDC.7 — LCD enable>), though it gets blanked out after a while.

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I think "stops updating" might confuse people, although it's technically correct.
I'm not sure what "gets blanked out after a while" means.

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AFAIK, leaving the screen turned off for a significant period of time causes the SGB firmware to blank out the framebuffer.

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@nitro2k01 nitro2k01 Oct 13, 2025

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I think there's a lot of detail that could be discovered through hardware research. Personally, I'd prefer to hold off on edits that go from saying something that's unconfirmed and maybe half correct to something else that's that's unconfirmed and maybe half correct. Especially when it comes to the SGB which is a device that both most people don't have access to, and isn't emulated 100% accurately, even in low level emulators that emulate the SNES portion of the equation.

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yep - at most we can (if deemed useful) put this into a "Rsearch needed" box and link to an issue that describes the theorized behavior etc

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also , blank out means forget, become unable to think, or cover/remove information - is this what you were going for @ISSOtm ?

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Do I need to call Cubby 🐻️ again for a test of how long it takes SGB to discard the last frame after LCD off?

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Well, then following Nitro's logic, we should not include the original claim at all either?

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Addition of that claim is tracked by #625, btw.

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SGB freeze-frame on LCD off should be mentioned

5 participants