There are two checksums in a jedec file created using CyberClocks software - CyberClocks checksum and the Jedec checksum
The CyberClocks software checksum is the one which is denoted, for example as:
# < Checksum: C818F4FC.
The JEDEC checksum is listed near the bottom of the file denoted for example as:
The CyberClocks checksum is used to verify that the JEDEC file contents have not been changed or corrupted and it can be read back into the software. If bits are modified or accidentally changed in the jedec file, you will get a checksum error and the jedec file canot be read back in CyberClocks software.
The box below the JEDEC checksum line is an "end of transmission" character and the four characters after that are a transmission checksum. CyberClocks fills it with 0's to disable the transmission checksum.
The newer jedec files will have a five digit jedec checksum and eight digit CyberClocks checksum as mentioned above. However, the jedec files created using the older software will have a four digit jedec checksum and seven digit CyberClocks checksum.
The easiest way to make sure an existing JEDEC file and newly generated JEDEC file are equivalent is to ignore the last line right above the checksum in the JEDEC file. The last line includes date and time stamp information that will change every time you generate a new JEDEC file.