MiSTer FPGA Forum

The Speccy core is lovely and seems to have everything except..... snapshot file support. This filetype was used on really early emulators. I think it predates .z80. I *think* it only supports the 48K speccy as well. Nonetheless, I have loads of games in this format.

https://faqwiki.zxnet.co.uk/wiki/SNA_format

Lawrence