conango
Posts: 5
Joined: 13 Aug 2020, 03:33

How to use srm files created by MegaSD to other emulators?

13 Aug 2020, 04:14

Hello, I'd like to continue some games on Wii's genesisGX Plus by using the MegaSD srm files.
On MegaSD, backup file per game was enabled, so I have separated srm files.
When I copied the files to Wii, it can't recognize the data.
I found 1 of the srm files is 41KB which not like normal 8KB or 16KB.
So I'm confused where the problems are, is there any way to make the separated srm files work on Wii's genesisGX Plus emulator?
Many thanks in advance.

conango
Posts: 5
Joined: 13 Aug 2020, 03:33

Re: How to use srm files created by MegaSD to other emulators?

31 Aug 2020, 02:06

I've heard of that the service of terraonion is bad, it seems true...
No official support at all.
In contrast, everdrive supports customers far more better.

User avatar
neodev
Posts: 452
Joined: 09 Apr 2018, 14:47

Re: How to use srm files created by MegaSD to other emulators?

31 Aug 2020, 16:46

There is no easy way to do that, as it depends on the emulator format. Some store only the meaningful bytes (those sram devices are 8 bit connected to a 16 bit bus, so only 8 bits are meaningful), other store words (with the high byte set to 0)

MegaSD stores only the meaningful bytes of internal and cart sram data in the same file:
4 bytes header
8KB internal megacd sram
the rest (16 or 32KB) ram cartridge sram,

so if you skip 4 bytes, then write the next 8KB to a file, and the remaining of the megasd save to another file, it might work in some emulator
as long as they store the meaningful (odd) bytes only. If they store the entire word, then you need to add a 0 byte before each byte (or after each byte if they store the data in little endian).

So, the data is the same, but the format may vary. MegaSD saves are built for smallest size, and no for interoperability.


conango
Posts: 5
Joined: 13 Aug 2020, 03:33

Re: How to use srm files created by MegaSD to other emulators?

01 Sep 2020, 08:26

Thanks so much, let me try this and report if it works or not.

conango
Posts: 5
Joined: 13 Aug 2020, 03:33

Re: How to use srm files created by MegaSD to other emulators?

03 Sep 2020, 02:02

neodev wrote:
31 Aug 2020, 16:46

8KB internal megacd sram
the rest (16 or 32KB) ram cartridge sram,
Hey, I'm so excited that I did it by following your instruction!
For the emulator on Wii, the 32KB ram cartridge file works!
8KB internal megacd file doesn't work, might need to fill with 0 to a 16KB file.

I'll try to make a tool for this when I have time.
Thanks again!

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