Re: Searching for an assembly guru -- DART disk utility

>BLU gets the format byte from the sector header, as stored in the
>disk controller's "VolFnd" aka "DiskID" variable when it reads a
>disk.

I should note that while this is true for 3.5" disk images, it isn't true for Twiggy disk images: When creating a Twiggy image from a disk, BLU uses the invented value of $01 instead of what is read from the disk header. (The objective was to make it more likely that software similar to DiskCopy would realize the disk image is not something they are familiar with.)

When BLU writes a disk image to the disk, it does not change the sector headers from what was put on the disk by a format operation.

However, when writing an image with, eg. a 400k format byte, BLU will complain if the disk was formatted with something other than the 400k format byte.

I see BLU accepts an alternate format byte of $FF in 800k disk images... I must have run across those somewhere, but I don't recall the details.

The format byte is used, eg. by BLU and MacWorks Plus, to recognize that a single sided disk has been put in a double sided drive and vice-versa.

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