I'm thinking more of the current situation where I want to load the image from SPI on boot and it looks like the ROM already reads in 256 longs (with checksum) so all I want it to do is also check for an SPI image size in that so it can continue to read from SPI into RAM. However the booter seems to be reading and checking the 32-byte signature, is that really necessary?
That 32-byte signature is gone, along with fuses and SHA-256/HMAC. Now we just need a single long checksum somewhere in the first 256 longs for the SPI to boot. If you go to the FPGA Files thread, you can click to the v25 docs in the first post. I just updated it an hour ago. Go to the end of the Google Docs file and see the latest booter sequence.
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That 32-byte signature is gone, along with fuses and SHA-256/HMAC. Now we just need a single long checksum somewhere in the first 256 longs for the SPI to boot. If you go to the FPGA Files thread, you can click to the v25 docs in the first post. I just updated it an hour ago. Go to the end of the Google Docs file and see the latest booter sequence.