4 ms·

the way to low-level format early MFM drives was to run DEBUG and enter assembly and call some special routine in the controller chip on the drive. These were i

• lproven 5y ago
  DEBUG g=c800:5 From 30-year-old memory. Yes, we actually had to do stuff like this. When I started my first job in the late 1980s, it was normal for hard disks to have a little label with a list of the (known) bad blocks on the drive. (Hand-written by someone at the factory on the first (circa 15-20MB) disks I used; later, on things like big ESDI disks, dot-matrix printed.) In some formatting tools, you had to manually enter them; formats took a long time, so eliminating retries on bad blocks could save half an hour. Novell Netware came with its own low-level formatter called `COMPSURF`: COMPrehensive SURFace analysis. Dozens of people would be sharing a server's hard disk, so data losses would be extra-bad -- and might well bring down the server, losing everyone's work. Note: the assumption in the early days of Novell was that workstations didn't have hard disks of their own and booted off the server too, making a LAN tens of thousands of £/$ cheaper than giving everyone their own HDD. Running COMPSURF before you installed took hours. Server HDDs were big -- hundreds of megabytes! Scanning all that took ages.