Real-life testing on the real hardware showed that some sprites were tearing. This effect is not correctly emulated by MAME and is due to drawing "too late".
When the Vertical Blanking Interrupt is emitted, the monitor's electron gun moves from the bottom-right corner back to the top-left. This journey takes 4550 cycles (4.5µs).
Then, it starts drawing line by line, and each line takes 65 cycles (6.5µs) to draw.
Reference: https://rich12345.tripod.com/aiivideo/vbl.html
So one should start drawing the highest things first.
Technical commit: https://github.com/colinleroy/a2tools/commit/af406473bb9940687f01b8c8dea898740c9d9bce
- draw dashboard on odd frames
- draw first, think later
- draw the lowest-Y sprites first
Colin McMillen
npub1x7…v58s2
2025-02-24 17:40:02 UTC
in reply to nevent1q…y3pv
Author Public Key
npub1x7qtesf7vnczj5uu3s2anz68hvq3lt7n6c2t49cm2090j4y5defq2v58s2Seen on
wss://relay.momostr.pinkPublished at
2025-02-24 17:40:02 UTCEvent JSON
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"content": "Real-life testing on the real hardware showed that some sprites were tearing. This effect is not correctly emulated by MAME and is due to drawing \"too late\".\n\nWhen the Vertical Blanking Interrupt is emitted, the monitor's electron gun moves from the bottom-right corner back to the top-left. This journey takes 4550 cycles (4.5µs).\n\nThen, it starts drawing line by line, and each line takes 65 cycles (6.5µs) to draw.\nReference: https://rich12345.tripod.com/aiivideo/vbl.html\n\nSo one should start drawing the highest things first.\n\nTechnical commit: https://github.com/colinleroy/a2tools/commit/af406473bb9940687f01b8c8dea898740c9d9bce\n\n- draw dashboard on odd frames\n- draw first, think later\n- draw the lowest-Y sprites first",
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