Hello Ruud, * On Thu, Oct 22, 2020 at 05:10:42AM +0000 Baltissen, GJPAA (Ruud) wrote: > > Thus, it's unclear if the resulting patched ROM is 4040/2031 compatible or > not. > > The difference is the size of bytes in the gap between the header and the data. > IIRC the -02 ROM and earlier have 8 bytes, the -03 nine. Your memory is right. The 4040 wrote a gap of 8 GCR byte (that is, 10 "raw" byte), while the 2031 used 8 "raw" byte. > Reading should never > be a problem. According several sources writing can. I myself cannot remember > having any trouble when using 4040 disks in a 1541 and vice versa. But that was > before I heard about the possible problem. The problem should be there only if using a 4040 disk in a 2031, 1540 or 1541 with a -01 or -02 ROM ("very early 1541"), as these have the 8 byte gap [*] The 9 byte gap seems to be a good compromise to be compatible with both the 4040 as well as with the 2031/1540/"very early 1541". To be more precise: The problem is when writing a disk in the 4040 drive, as it will leave a bigger gap than the 2031/1540 and it will be already in the SYNC mark when starting to write. Contrary, writing a disk formatted in a 4040 with the 2031/1540 should not be a problem, as the floppy just starts writing earlier. Of course, if writing the block over and over again, from the different drives (the BAM block comes to mind) might have its own rules... Regards, Spiro. -- Spiro R. Trikaliotis https://spiro.trikaliotis.net/Received on 2020-10-28 08:00:03
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