neosd
Neosd Developer
- Joined
- Oct 18, 2016
- Posts
- 956
Ok one more question in relation to what you said about MSX. You say your patching the game on fly with the fpgas. Does this mean its patching in real time at the point the game is written to flash memory (so the flash is patched), or while the game is playing on the NeoGeo? I guess I'm asking if your cart is intercepting all reads to the program ROM space (0x00000-0xFFFFF) and then returning different values (than that in flash) for some addresses only, to give different opcodes to circumvent the protection?
Hello Again,
About Metal Slug X :
The fpga intercepts the read of specific addresses and returns a different opcode (nop) so it's bypassed. Because the cartridge can't know if it's a read or an opcode fetch, it will make the unibios crc fail, as it will see the modified opcodes as it scans the rom to compute the crc.
We dont patch anything on the rom neither on the flashes.
Think that on a regular basis, we could deliver the flashcart bypassing the protection as it does right now and no one would care about as long as the game is playable, but our goal is to make a perfect solution to people that love the system as much as we do.
This is the main reason we have adopted this design, we want to have 100% the same function the real cartridge delivers.
Thanks !
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