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MiSTer-devel / Atari7800_MiSTer

Atari 7800 for MiSTer
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Role of the FBLN memory in video_mux? #26

Closed gyurco closed 6 months ago

gyurco commented 6 months ago

I'm checking through the BRAM usage of the core, and I don't understand this one in video_mux: https://github.com/MiSTer-devel/Atari7800_MiSTer/blob/13a5ce43cd0e0bc15a677bffe0f0578498fcfc53/rtl/video_mux.sv#L65

It's a single ported RAM, no double buffer, nothing uses the 'past' pixels, only the last one for composite blending emulation. Was it used for something else, then maybe lost its job?

I can get the same effect with this patch in my fork: https://github.com/gyurco/Atari7800_FPGA/commit/950c9d5ed5d57a1db68f41eea1fc731f1c5ef962

Or am I overlooking something?

Kitrinx commented 6 months ago

I think this is an accidental leftover from an experiment I made trying to stabilize the frame from TIA. I can't quite remember what I was doing there but at a glance it seems like it does nothing of importance.

gyurco commented 6 months ago

Thanks for confirming. Are you interested in a PR to clean this up? I also have some more, like supporting cart ram in SDRAM and make the SDRAM timing conform to the datasheet (tRCD=2, not 1 @57MHz) without breaking DMA.

Kitrinx commented 6 months ago

Yes by all means, your contributions are welcomed.

gyurco commented 6 months ago

I issued a PR: https://github.com/MiSTer-devel/Atari7800_MiSTer/pull/27