1 Feb
2022
1 Feb
'22
2:08 p.m.
On 2/1/22 13:40, Paul Koning via cctalk wrote:
With MSCP, DEC switched to addressing disks by sector
offset, as SCSI did later, rather than by geometry (cylinder, track, sector) on devices
like the RK05 and RP06. If the OS sees only an LBA, it doesn't matter whether the
drive uses zone recording; such complexity can be hidden inside the controller firmware.
But I don't know if that was actually done, either at that time or in later
generations.
Good grief, it took DEC all that time? CDC was doing it in the 1960s.
Had to, because of the wide variety of RMS available. I think that
one of the early 2311 clone drives (854?) used 256-byte (8 bit byte)
hard-sectored media, which isn't very friendly to systems with 60 bit
words. I recall that several sectors were used to create a logical
60-bit word addressable sector, with a substantial part of the last
sector of a logical PRU left unused.
--Chuck