ROM padding question

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Sik
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Re: ROM padding question

Post by Sik » Fri Aug 18, 2017 8:28 pm

Stef wrote:
Fri Aug 18, 2017 11:28 am
ROM padding is here for some reason though, unpadded ROM won't work on some flash cart.
Specifically, unpadded ROMs get misdetected as being SMD format by the firmware some flashcarts which then will attempt to deinterlace it. I only saw it happen with small ROMs though, although I guess it could still happen with larger ROMs.

Also the part that honestly you don't want mirroring to be unpredictable.
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Re: ROM padding question

Post by Manveru » Sat Aug 19, 2017 5:38 am

I know the roms needs the padding. I just said to remove it for the purpose of this topic :wink:
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Re: ROM padding question

Post by Stef » Mon Aug 21, 2017 8:54 am

Yeah i know ;) I was just saying that for people who were wondering ;)

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Re: ROM padding question

Post by Chilly Willy » Tue Aug 22, 2017 4:25 pm

Sik wrote:
Fri Aug 18, 2017 8:28 pm
Specifically, unpadded ROMs get misdetected as being SMD format by the firmware some flashcarts which then will attempt to deinterlace it. I only saw it happen with small ROMs though, although I guess it could still happen with larger ROMs.
That's because some flash menus assume that if a rom isn't a power of two, there's a header at the start... instead of checking for a valid header to determine if there's a header at the start. :D

Actually, ALL SMD files will be a multiple of the SMD block size + size of the SMD header.
Also the part that honestly you don't want mirroring to be unpredictable.
That's the important thing... for games that use mirroring... which is weird - I never got why programmers ever used mirroring. The ONLY time it's handy is for like the Saturn DRAM cart where the smaller cart doesn't have the two banks of dram contiguous, but does mirror the dram. So by using a mirror of the 1st bank, it will be contiguous with the 2nd bank of dram giving one contiguous block of ram.

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Re: ROM padding question

Post by Sik » Tue Aug 22, 2017 7:53 pm

Chilly Willy wrote:
Tue Aug 22, 2017 4:25 pm
That's because some flash menus assume that if a rom isn't a power of two, there's a header at the start... instead of checking for a valid header to determine if there's a header at the start. :D

Actually, ALL SMD files will be a multiple of the SMD block size + size of the SMD header.
I think they may be checking for the latter actually, the issue I ran into once only happened on specific filesizes rather than any non-padded ROM. Still would be stupid to not look for the header instead (or heck, the file extension if we want to slack off, I've yet to see any SMD file that doesn't have the ".smd" extension so it's pretty much a safe assumption for practical purposes).
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Re: ROM padding question

Post by TmEE co.(TM) » Tue Aug 22, 2017 7:59 pm

SMD format files shouldn't exist at all, and all support for them should be removed IMO so that the format can die out...
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Re: ROM padding question

Post by Chilly Willy » Wed Aug 23, 2017 1:33 am

TmEE co.(TM) wrote:
Tue Aug 22, 2017 7:59 pm
SMD format files shouldn't exist at all, and all support for them should be removed IMO so that the format can die out...
QFT

It's a really bad format based on old byte wide rom dumpers. Unfortunately, when most of the MD flashcarts came out, that was the dominant format for Genesis rom dumps. It's since been replaced with a raw binary format, but you still see SMD support in menus for folks who never bothered to update their libraries. Not only is the format a pain, but it's so old that many of the games in SMD format are bad dumps... and some are hacked dumps. Most are not clean or verified.

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Re: ROM padding question

Post by Sik » Wed Aug 23, 2017 9:12 am

To be fair I don't think anything new supports SMD at all (neither new emulators nor new flashcarts), so it's possible the issue is gone by now. And I haven't seen SMD files in ages... except for that one stray SMD from a really old archive I had around that I had to convert to BIN with Genecyst first (because somehow, Genecyst is still useful as the swiss knife for older stuff without having to put any effort on thinking lol). I wouldn't be surprised if the Everdrives don't have support for SMD files.

The trend I'm seeing now is to rename every .bin file to .gen though =P (thankfully the attempts by some people to ditch raw dumps in favor of wrapped files with metadata haven't taken off, it'd be annoying to be required to switch formats because some homebrew refuses to follow the rules and nobody wants to make extensions to the existing ROM header)
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