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Thread: Super Castlevania IV FastROM Patch - Improves performance

  1. #31
    Master of Shinobi
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    Jun 2011
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    Quote Originally Posted by turboxray View Post
    Not true, actually. Even in 3.57mhz mode, the SNES cpu has extra cycle penalties for 16bit mode operations, not to mention that work ram is always 2.68mhz - and the 65x pretty much being a Read-modify-write type processor hits ram for already every instruction and for multiple bus cycles. It pretty much brings it down to 3.05mhz range. I clocked full 16bit and 16bit -> 16bit operations (not half cheating with early exit branches) on the PCE to be faster than the SNES. The only thing faster really is the multiply unit, but that's not the processor itself, and shift instructions.

    Honestly though, I wish someone would run a cpu analysis on these games when they're running, just to see how much the cpu overblows the vsync flag 'window'. For some of these games, it literally just could be like 2-3% cpu resource over the limit, because it's an all or nothing thing for the frame rate for the game logic.

    If you're talking about the nes2pce games I did, they run at PCE's full speed because they emulate/simulate the NES video and audio hardware in realtime. Even with that overheard, the slowdown is removed from the games running on PCE haha. Vsync keeps the games running in sync, but special timed code for sprite detect 0 has to be manually fixed in the rom to compensate.
    Oh hey, I didn't realize that was your work! Very impressive. And wow I am surprised the SNES CPU is *that* bad.

  2. #32
    Hedgehog-in-Training Hedgehog-in-TrainingRoad Rasher
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    Dec 2019
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    Quote Originally Posted by axel View Post
    Oh hey, I didn't realize that was your work! Very impressive. And wow I am surprised the SNES CPU is *that* bad.
    I mean, there are areas where it's faster.. or just easier, like doing things like $0000,y which is basically [Y]. That's kinda nice. Long addressing (direct and indirect) is also nice, even if a little more expensive. A 7mhz version of the processor would have been incredible haha, even with the 8bit data bus.

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