sd2iec binaries source
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It appears that some sellers of devices with sd2iec, especially on auction sites like eBay, claim that sd2iec is a "1541 emulator". They are lying. sd2iec is not, has never been and will never be a 1541 emulator - it merely provides access to an SD card using the same commands used by Commodore disk drives. To qualify as a 1541 emulator, a device must be able to run the actual program code that is running on the processor of a 1541. sd2iec does not do this at all and there are no plans to change that.
Demos, games and other programs that attempt to run custom program code on the drive's processor (e.g. to speed up loading or to validate copy protection) do not work with sd2iec, as it does not emulate a 1541. sd2iec only manages to be compatible with a small number of fast loaders because each one of these has been manually analyzed and reimplemented to make sd2iec speak the same protocol. Since this is a very labor-intensive process, it is unlikely that the random loader/copy protection of the game/demo/application that you care about will ever be supported in the same way.
If you need full compatibility with any random disk image, get a device that actually is a 1541 emulator. If you just need easy access to some files stored directly on the SD card or within D64/D71/D81 images but without anything that requires actual 1541 emulation, sd2iec may be right for you.
Don't get fooled by eBay scammers: sd2iec is not a 1541 emulator.