Size limits

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Hpman
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Re: Size limits

Post by Hpman » Thu May 02, 2019 3:52 pm

What's going on exactly on A130EC with 32X?
Had a quick look online, games do read there for a keyword (so effectively EC-EF), but mapper is only dealing with writes, not reads.I am missing something there ? :?

Also are the standard board holes exact potitions available somewhere? Thoses are quite off :D

Sik
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Re: Size limits

Post by Sik » Thu May 02, 2019 3:57 pm

Potential for bus fights.

But yeah, $A130EC is a 32-bit register that returns "MARS" when read and nothing else. Its only purpose is to allow detection of a 32X.
Sik is pronounced as "seek", not as "sick".

Hpman
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Re: Size limits

Post by Hpman » Thu May 02, 2019 4:03 pm

Isn't 32X just masking this range? A130EC read (also write?) will just never make it to the cartridge, right?

BTW does SSF2 mapper return something when reading its range?

Sik
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Re: Size limits

Post by Sik » Thu May 02, 2019 4:09 pm

Hpman wrote:
Thu May 02, 2019 4:03 pm
Isn't 32X just masking this range? A130EC read (also write?) will just never make it to the cartridge, right?
Yeah, that's what I said earlier, and I mentioned some games that use $A130F1 map all of $A130xx to it, and as far as I'm aware Sonic 3 (& Knuckles) doesn't have problems with the 32X despite that, and I don't recall hearing Phantasy Star IV being a problem either. Can somebody confirm? (EDIT: I suppose those games never implement reading from it either…)
Hpman wrote:
Thu May 02, 2019 4:03 pm
BTW does SSF2 mapper return something when reading its range?
The docs we have only seem to say $A130F1 is write-only while not explicitly saying anything about the rest (unless there's a translation snafu with the grammar and the note applied to all registers)… but as far as I'm aware, the whole thing is write-only.
Sik is pronounced as "seek", not as "sick".

Chilly Willy
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Re: Size limits

Post by Chilly Willy » Thu May 02, 2019 8:10 pm

Hmm - I never thought of it that way, but yeah, because the 32X gets the address before the cart, it should be fine just decoding the least few bits. The 32X should pass through anything other than 0xA130EC. Thanks for pointing that out.

Sik
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Re: Size limits

Post by Sik » Fri May 03, 2019 2:09 am

Yeah, but later we were discussing about this in Plutiedev and the mapper is always write-only while the 32X register is always read-only (meaning that in theory, it's perfectly possible there's no conflict simply because they don't respond to the same strobes). Sounds like we'll need to make some tests to know for sure.
Sik is pronounced as "seek", not as "sick".

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