Got the Adler checksum to match. it needed a small change to the Ascii85 algorithm. Ordinarily in Ascii85 encoding, a 'z' character means four 0s (NULL bytes) and a 'y' character means four spaces. Well, in Apple's implementation of Ascii85, a 'y' character means four 0xFFs. Probably makes sense considering unprogrammed flash is 0xFF. I was barely able to comprehend that from the Forth code. It really is a foreign syntax to me!
Plus, the checksum algorithm runs past the end of the decoded data. The decoded ROM image is 264,868 bytes, but the checksum is run for 0x7FFFC (524,284) bytes. Once I padded the rest of the decoded data with zerosn so the total length is 524,284, the checksum came out perfectly.
The sound data at the end is still not sounding correct, so it must be compressed or encoded in some way...
Plus, the checksum algorithm runs past the end of the decoded data. The decoded ROM image is 264,868 bytes, but the checksum is run for 0x7FFFC (524,284) bytes. Once I padded the rest of the decoded data with zerosn so the total length is 524,284, the checksum came out perfectly.
The sound data at the end is still not sounding correct, so it must be compressed or encoded in some way...