@TheMogMiner recently made a very informative post about why CD-i emulation is so difficult and why it's unlikely to improve anytime soon. @Interact_Dreams summed it up nicely here, I recommend anyone who asks about the subject to give it a read. https://cdii.blogspot.com/2021/03/the-developer-behind-mame-cd-i.html …
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I think I don't fully understand this post. I thought everything going through a system library with a well defined spec but flexible implementation made things much EASIER to emulate, just by substituting your own library implementation?
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That's not how emulation works.
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Vastauksena käyttäjille @TheMogMiner, @MrCheeze_ ja
Emulation doesn't work by "substituting [a] library implementation". Quite the opposite, it's 100% agnostic to the software itself. A well-made emulator reproduces the functionality of the underlying *hardware* as accurately as possible, with no consideration of the software.
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Vastauksena käyttäjille @TheMogMiner, @MrCheeze_ ja
As I explained in the earlier Twitter thread, when software bangs on the hardware directly, it makes it somewhat easier to tease out the nuances of the hardware's functions, as each developer tended to be subtly different in terms of their code.
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Hmm. My impression was that Nintendo's N64 emulator does exactly that, hooking into and replacing system library calls with native code for the emulating platform. For a system like CDi where the hardware is *intentionally* unspecified, it seems potentially fruitful?
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You're thinking of high-level emulation (HLE), which was pioneered in the late 90's with the N64 emulator, UltraHLE. Nintendo went that route for Virtual Console primarily for speed reasons, not due to a lack of hardware documentation on their part.
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Vastauksena käyttäjille @TheMogMiner, @MrCheeze_ ja
It's not quite as simple as just dropping in a new library, and away you go. The N64 had a vector coprocessor (the RSP) which handled the calculation side of both the graphics and audio stack. HLE-ing the N64 still required reverse-engineering the routines uploaded to the RSP.
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Vastauksena käyttäjille @TheMogMiner, @MrCheeze_ ja
Overall, there were roughly 20-40 unique sets of microcode routines. Some were used by only one or two games, some were used by a fairly large chunk. So it's not entirely the same situation with the CD-i.
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For what it's worth, another person replying to @thedopster did mention the same thing - that it should theoretically be more straightforward to HLE the CD-i than do it bare-metal - but also accurately gauged that that method is a no-go for MAME.
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Vastauksena käyttäjille @TheMogMiner, @MrCheeze_ ja
MAME doesn't go the HLE route when emulating the N64, either, as the stated goal of the project is to at least attempt to emulate things as accurately as possible. HLE is generally only invoked as a last resort, and we're not even near last-resort territory with the CD-i.
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Vastauksena käyttäjille @TheMogMiner, @MrCheeze_ ja
People far more skilled at reverse-engineering than I am have gotten far more information about systems far more complex than the CD-i and gone the low-level emulation route in MAME. The simple reality is that I haven't had the time or energy to knuckle down and just do it.
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