Winchester Drive

A colleague at work gave me a Seagate ST-225 "winchester" MFM hard disk.  This disk is the same as the RD31 used in PDP-11's (a 20meg drive). It has been sitting inside my PDP for a while, but I could not format it.  I tried to make an XXDP boot disk, which has the formatting program, but it halted the machine when I tried to use it.  RT-11 cannot format fixed disks.  However, I managed to find other means to get XXDP onto my machine.  Here is the disk format program in action:

ST-225 MFM formatting

Nice!  What I did was boot XXDP in the SIMH emulator, start the ZRQCH0 formatting program and then dump the first 56k of memory to disk.  I then used a little C# utility I wrote to turn this dump into machine instrictions that could be entered into memory via ODT.  It took about 2 hours to send the data over a 9,600 baud serial line.  Still, it worked a treat!  I have a formatted hard disk in my machine!  I haven't managed to make it bootable yet, but I have copied some files to the new disk.  I need to upload some photos...