tomb@tekecs.UUCP (Tom Beach) (07/11/85)
This is a second attempt at this posting. I believe that the first one, tried 1 week ago, failed. My apologies if this is duplicated for some of you. * * * * * * * * TEXT * * * * * * * * First of all, some history. SASI is the predecessor of SCSI and no longer exists as a supported specification. The organization which initiated it (Shugart Associates) no longer exists and was not supporting it on any current products at the time of their demise. It's last champion was Xebec and even they are entering the 20 th century and moving towards support of SCSI. SCSI is being worked up by an ANSI comittee. X3T9.2 It is currently in rev 14 which I understand has been or will soon be submitted to the full ANSI group for approval. IT IS A REAL STANDARD *** With Caveats **** Caveats: Like many (most?) other I/O class standards it supports "vendor specific" commands which opens the door for a particular vendor to incorporate "features" and extend the standard. Drives which have been announced, or are actually available with integrated SCSI interfaces include Winchester disks, Optical disks, and Cartridge tape drives. Controllers using SCSI interface are available for PerTec I/F 9-track tapes, SMD disks, ST506 and ESDI winchester disks, cartridge tape, flexible disks, and various combinations of the above. SCSI is fast becoming the interface of choice for Medium size system mass storage connection. One area of concern is the graceful handling of media defects. With defect specs running an allowed 1 defect / unformatted MByte of capacity. (e.g. 67 defects allowed on a 67 MB drive) How these are mapped, and how "new" defects are handled becomes an important consideration and since this is largely hidden from the user, it is being done in a myriad of strange and wonderful ways, some intelligent, some ?????. I have had good luck in using only the REV 14 required, extended and optional commands in SCSI drivers. We have Streaming Tape drive controllers for the 5 1/4" DC 300 XL tape drives from three different vendors which work with a single driver. I can't find my reference to order a copy of the document, sorry. Tom Beach Tektronix Inc PO box 1000, MS 61-201 Wilsonville, Or 97070 email: ...!tektronix!tekecs!tomb -- Tom Beach email: ..tektronix!tekecs!tomb