> On Sep 14, 2017, at 4:47 PM, Warner Losh <i...@bsdimp.com> wrote: > > > > On Thu, Sep 14, 2017 at 2:44 PM, Paul Koning <paulkon...@comcast.net > <mailto:paulkon...@comcast.net>> wrote: > > > On Sep 14, 2017, at 4:39 PM, Warner Losh <i...@bsdimp.com > > <mailto:i...@bsdimp.com>> wrote: > > > > ... > > I don't see where you read the first 2 tracks uninterlaced, and the other > > tracks interlaced? For DOS formatted disks, that's what's required. While > > screwing up the first two tracks won't affect your ability to read DOS > > floppies (since they were reserved for the boot blocks), other formats > > aren't so forgiving and it makes the disk unbootable... > > The question was about RX50 disks, which are uniformly interlaced and skewed. > > No. They are not. CP/M MS-DOS on the Rainbow didn't do it uniformly. Venix on > the Rainbow did it a different way. They are not uniform, and the first two > tracks were not skewed. The DECMATE did it differently (not skewing tracks 78 > and 79). I'm unsure how other OSes handled things, but it was anything but > uniform. > > I wrote IMPDRIVE back in the day to read 3.5" floppies and had to cope with > this. I have the BIOS listing for MS-DOS that shows clearly that the first > two tracks weren't skewed. I also have the CP/M listing, but don't have it as > handy. I'm quite certain of the non-uniformity.
I guess I missed the fact that Rainbow did things differently. What I said is valid for MSCP and Pro RX50s. Thanks for the correction. paul