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Blogs

Transcode Audit Session #1

January 31, 2023 Retro Ports

Tonight I started on the “audit” of the transcode. What I mean by this is a line-by-line review of the transcode, checking for: consistency between Z80 and 68K codeconsistency between Z80 and 68K annotationsmissing logic/code from 68K transcodemicro-optmisations of 68K code I’m only a very short way into the MAIN …

Blogs

Neo Geo implementation complete (transcode bugs aside)!!!

January 28, 2023 Retro Ports

Sprite optimisation is – to the best of my knowledge – complete! I had some time tonight to look at 2×2 tile sprite flipping, noticed that in my previous “shortcut” attempt I had made an error, fixed it… and it worked! I also verified that 1×2 sprites are never Y-flipped, …

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Blogs

This is taking a flipping long time!

January 27, 2023 Retro Ports

Scant time again but have managed to do some more sprite optimisation. Technically, there’s plenty of time to update the shadow registers before the next VBLANK, but I don’t like unneceessarily inefficient code. I’ve done some optimisation as far as the current functionality is concerned, and I’m happy with that …

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Blogs

When less sprites is more… good!

January 23, 2023 Retro Ports

Just time for a quick ‘n’ dirty fix to the sprites, and already looking a lot better! Each Xevious sprite has 2 Neo Geo sprites allocated, because the Xevious hardware can select double-width and double-height sprites. I thought I had coded the logic to deactivate the 2nd sprite for the …

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Blogs

Scrolling complete; only sprites to optimise now!

January 22, 2023 Retro Ports

I’m happy enough with the scrolling on the Neo Geo now so I can move on. I could probably squeeze a few more cycles from the case where the scroll register is updated with a completely arbitrary value, (as opposed to scrolling the screen 1 pixel), but there’s no point …

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Blogs

Scrolling optimisation WIP

January 17, 2023 Retro Ports

Quick update. Didn’t really have the time to spare to work on Xevious tonight, but I did anyway, I have optimised the scrolling in the 2 cases where it scrolls down by 1 pixel (map row boundaries being the 2nd case) – ie. 99.99% of the time. I didn’t get …

Blogs

Time is an illusion, Xevious time doubly so!

January 14, 2023 Retro Ports

Lack of progess is not due to lack of motivation, but lack of time. From holidays back to work with a new boss and new tasks, kids needing to be entertained during the holidays, and training for a bike ride that is coming up all too soon… leaving absolutely no …

Blogs

Looking good on the AES!

January 7, 2023 Retro Ports

I’ve fixed the black line (missing tiles) issue on the background. Turns out you need a rather lengthy delay after setting the VRAM address register before you attempt to read from VRAM. Much better to avoid having to read altogether, so I re-wrote the background color/video RAM access routines from …

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Blogs

Running on an AES again… good news… and bad news.

January 6, 2023 Retro Ports

I ran the latest build of Xevious on my AES… and some very unexpected results!!! First and foremost, the VBLANK ISR is running to completion during the vertical blanking period (no red line on the display). I have confirmed with a delay loop that extending the ISR does result in …

Blogs

I’m not seeing red, but that’s not a good thing!

January 5, 2023 Retro Ports

Some more optimisations today; look-up tables for foreground and background video sprite tile (SCB1) addresses per memory address. Looking at the online profiler again, I’ve decided I can’t make much sense of the numbers that it is reporting. It may have something to do with the RED numbers on half …