agnew@trwrc.UUCP (R.A. Agnew) (08/26/87)
Would someone please explain the difference between SCSI and SASI. Please spare the History. What's the difference in data rate and protocol? I notice that pins are the same. It would be nice to be able to use the SASI as the controllers are only $14 at Halted Specialties.
jjg@walden.UUCP (John Grana) (09/08/87)
In article <211@trwrc.UUCP> agnew@trwrc.UUCP (R.A. Agnew) writes: >Would someone please explain the difference between SCSI and SASI. >Please spare the History. What's the difference in data rate and >protocol? I notice that pins are the same. It would be nice to >be able to use the SASI as the controllers are only $14 at >Halted Specialties. Sparing history (other then SCSI "grew" from SASI), here are some of the key differences: data rate: SCSI - 1.5 Mb/Sec async 4 Mb/sec sync SASI - ??? (im not sure probably around 1 SASI - no sync support protocol: SCSI - has message passing protocol that allows disconnects (during seeks/rewinds/etc), data retries (i.e. restore pointers) - supports arbitration for the "bus". This allows multiple initiators and controllers; also key for disconnect/reconnect. SASI - the only message it supports (I think..) is command complete. - does not support arbitration. Overall, SCSI is a more "mature" version of SASI. Yes, the bus signals are the same (both electrical/functional). Thus, you could run a SASI controller off a SCSI host adapter, but I don't think a SCSI controller would run well off a SASI host adapter. Also, for what its worth, the SCSI protocol is "defined" by ANSI and is implemented better by various manufacturers. SASI was described by Shugart and its implementation may vary between different controllers. john grana ..!rochester!cci632!walden!jjg