149. When is a 1770 FDC not a 1770? ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ When it's a 1772! My Master would not work properly with an old Teac full-height drive. I tried using both *CONFIGURE FDRIVE and *FX255 to select 30ms head-step time to suit the slow drive, but that made matters worse. On examining the FDC, (Floppy Disc Controller), chip in my Master, I discovered it was a 1772 and not a 1770. Page C.5-4 of Part 1 of the Reference Manual has a little table relating to the *CO. FDRIVE parameter:- Value Head Step Time Precompensation (WD1770) (WD1772) (ADFS only) 0 or 4 6ms 6ms yes 1 or 5 6ms 6ms no 2 or 6 30ms 3ms yes 3 or 7 30ms 3ms no The normal values to use are 0 or 2, but instead of increasing the step time from 6ms to 30ms, I was actually decreasing it to 3ms! Most 80-track drives will work fine on 6ms, and many are OK on 3ms, though not when switched to 40-track mode, (due to the double-stepping), but many older 40-drives won't work on either. This is a bit naughty of Acorn, as it could force Master buyers to change their drives. Whilst there are considerable advantages in upgrading to double-sided 80-track drives, people ought to be able to do this when they are good and ready! If you want to check which FDC chip is fitted, take the lid off, and peer under the back of the keyboard, more-or-less under the red key. You'll need a torch, and the keyboard ribbon cable does get in the way a bit!