On Thu, Sep 14, 2017 at 2:50 PM, Paul Koning <paulkon...@comcast.net> wrote:
> > 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> > wrote: > >> >> > On Sep 14, 2017, at 4:39 PM, Warner Losh <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. > Never used a Pro... If the guy has a Rainbow and needs to make copies of the disks, his best bet is to do it with rbimg, in phyisical mode and to buy old new media to receive the copies. There's several places on ebay that sells the 96TPI quad (not high) density media that works the best and that the Rainbow can format. I bought 20 disks recently for the Rainbow Venix copies I made for someone on the list... Hopefully, he doesn't also need a UNZIP program :) Warner
