The other day I made the MFM emulator pretend to be a shiny new Maxtor XT1140. I did it by creating a new file full of zeros and then using mfm_util to turn it into an .emu file.
As it happens, the mfm_util program cannot create a new .emu file with the format that our computer requires. Fortunately, I have a utility disk with a low-level formatter. I simply created an .emu file in a different format, did a low-level format with the utility disk, and now the image is ready to go.
Everything is working great. I'm now wondering though if I can update the metadata in the .emu file so that it describes the new format and not the old. Right now the metadata says that the disk is:
--heads 15 --cylinders 918 --sectors 17,0
0xffff,0x1021,16,0 --data_crc 0xffff,0x1021,16,0
But if you try to run mfm_util against the image, you get grievous errors since that information is out of date. What you need to tell mfm_util instead is
--heads 15 --cylinders 918 --sectors 18,0
--header_crc 0x0,0x1021,16,0 --data_crc 0x0,0xa00805,32,5
It looks like the metadata is just text at the top of the .emu file, and I could hack in the new parameters with a binary editor. That feels risky, though. Also, while I know that --sector_length 512 is correct, I'm not sure how to specify --track_words. Is there a right way to change this information?