On Mon 29 Sep 2025 at 09:32:01 +0200, Francesco Messineo wrote: > On Sun, Sep 28, 2025 at 10:37?PM André Fachat <afachat_at_gmx.de> wrote: > > > > > > It could very well be that there is a difference in gap length between formatting a disk and writing a sector. Those are two different code paths IIRC. > > yes, this is what I'm observing on the 4040 formatted floppy. I was > just curious to know if someone can identify what is going on on the > actual code. I tried looking for the source code at https://github.com/mist64/cbmsrc, but even though there is the controller code for 8250 (https://github.com/mist64/cbmsrc/blob/master/CONTROLLER_8250/cmds for the code that writes a sector) (which seems to use variable gap sizes, so looking at just the source code there isn't even telling what the gap sizes are), there is no CONTROLLER_4040 directory. What is also missing is the source code for the formatting. It is run by the fdc cpu too, but it doesn't fit in the 2 KB of ROM that it has available. So it is part of the main CPU's rom and copied into buffer RAM when needed. For that purpose it is separately assembled and overlaid onto the ROM later; but this is not present in the repository's build procedure and the source for this is missing. There is more missing: the power up initialization of the FDC, which is also not present in the FDC ROM itself for the same reason. For these we will have to rely on disassemblies. > Frank -Olaf. -- ___ Olaf 'Rhialto' Seibert <rhialto/at/falu.nl> \X/ There is no AI. There is just someone else's work. --I. Rose
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