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Amiga Hardware Issues and discussion / Re: I made a modified accelerator, it works, but has a problem
« Last post by r00tb33r on April 19, 2024, 09:31:37 AM »shouldn't the vblank frequency be 60Hz for NTSC? Yours runs at half speed.Yep, exactly half reported by ATK. With the unmodified accelerator at 14MHz it reports a reasonable 59.83Hz. Interestingly SysInfo measures the correct 60 unlike ATK, presumably using a different timer. At 21MHz ATK measures some even crazier number like 39Hz. So the faster it goes the lower vblank frequency it measures.
Because the timers are running too fast, the measued frequency is too low.That is my understanding.
Something I hadn't tested up until this point, I had KS 1.3 ROM in there this whole time, because 500 rev.5 has the oopsie mistake on the board, I finally installed and wired up correctly the KS 3.1 ROM, and unlike 1.3 this one does not boot from the Gotek floppy at either 21 and 28MHz... So that's a newly discovered problem #2, though very high likelihood it is related to the same interrupt/timer problem. Obviously I will need to revert to KS 1.3 ROM to run ATK for further testing until these interrupt timers are ironed out.
I feel like I'm so close... Just wish I knew what rogue signal causes the speedup.