add@sciences.sdsu.edu (James D. Murray) (06/18/91)
I'd like to know if the SCSI-2 spec defines the data encoding method to be used with SCSI drives. SCSI drives use RLL encoding, but do they ever use ARLL encoding? Howz about drives for use with SCSI-2 systems? -- -------------------- add@sciences.sdsu.edu
k2@bl.physik.tu-muenchen.de (Klaus Steinberger) (06/18/91)
add@sciences.sdsu.edu (James D. Murray) writes: > I'd like to know if the SCSI-2 spec defines the data encoding method >to be used with SCSI drives. SCSI drives use RLL encoding, but do they >ever use ARLL encoding? Howz about drives for use with SCSI-2 systems? SCSI never defines the data encoding on a drive. It's really independent from the data encoding. The SCSI BUS transfers bytes, not encoded data. The drive itself has to deal with the encoding. The bus is completely independent from data encoding. So it's possible, to not even connect disk drives, you can also connect tapes, printers, scanner, or whatever you think about. (Maybe your computerized toaster) Sincerely, Klaus Steinberger -- Klaus Steinberger Beschleunigerlabor der TU und LMU Muenchen Phone: (+49 89)3209 4287 Hochschulgelaende FAX: (+49 89)3209 4280 D-8046 Garching, Germany BITNET: K2@DGABLG5P Internet: k2@bl.physik.tu-muenchen.de
Roger.Sheppard@actrix.gen.nz (Roger Sheppard) (06/18/91)
In article <1991Jun18.001914.21305@sciences.sdsu.edu> add@sciences.sdsu.edu (James D. Murray) writes: > > I'd like to know if the SCSI-2 spec defines the data encoding method > to be used with SCSI drives. SCSI drives use RLL encoding, but do they > ever use ARLL encoding? Howz about drives for use with SCSI-2 systems? > > -- > > -------------------- > > add@sciences.sdsu.edu There is one Drive that I think uses ERLL or ARLL, this is a Kaylock, I am not to sure how its spelt ,a SCSI drive, I did ask the Importers here, and they told me that the 40 meg SCSI drive was the same Mechanism as the 20 meg drive. -- *** Roger W. Sheppard * Roger.Sheppard@bbs.actrix.gen.nz *** *** 85 Donovan Rd * * At least I don't Flicker, not *** *** Kapiti New Zealand.. * like a dying light globe. ! ***
colin@array.UUCP (Colin Plumb) (06/19/91)
In article <1991Jun18.001914.21305@sciences.sdsu.edu> add@sciences.sdsu.edu (James D. Murray) writes: > > I'd like to know if the SCSI-2 spec defines the data encoding method >to be used with SCSI drives. SCSI drives use RLL encoding, but do they >ever use ARLL encoding? How about drives for use with SCSI-2 systems? No SCSI spec (SCSI-1 or SCSI-2) define in any way the data encoding. You could have a genie in there writing in Babylonian cuneiform on clay tablets and conform to the letter of the SCSI spec, if you could get him working fast enough to avoid timeouts. All you have to have is a bunch of blocks that can be read or written with a consistent number of bytes each. Because they aren't handicapped by a user-visible encoding (unlike ST-506 and its ilk), SCSI drives (even where they're so staid as to use horizontally magnetised, multi-layer discs for media) show more variety. MFM (also known as (1,3) RLL) is used, but the RLL used by so-called "RLL controllers" for IBM PCs, namely (2,7) RLL is also used, and (1,7) RLL is very popular. -- -Colin