Path: utzoo!utgpu!jarvis.csri.toronto.edu!mailrus!iuvax!rutgers!bpa!cbmvax!grr From: grr@cbmvax.UUCP (George Robbins) Newsgroups: comp.sys.dec Subject: Re: DEC 3100 drive question??? Message-ID: <6686@cbmvax.UUCP> Date: 25 Apr 89 19:24:16 GMT References: <905@uceng.UC.EDU> <2670@decuac.DEC.COM> Reply-To: grr@cbmvax.UUCP (George Robbins) Organization: Commodore Technology, West Chester, PA Lines: 40 In article <2670@decuac.DEC.COM> avolio@decuac.dec.com (Frederick M. Avolio) writes: > In article , jwg1@bunny.gte.com (James W. Gish) writes: > > According to our local DEC salesman, there are currently no third > > party drives available for the 3100, i.e., you might call it > > pseudo-SCSI. > > Of course this is not true. Or maybe you were tongue-in-cheek? You just > need to find a SCSI drive that sticks to the specs. We've run quite > a few different company's SCSI devices. There was a discussion of > this in comp.unix.ultrix a while back. Perhaps someone who saved the info > could send it to you? I am cross-posting this reply to there. It is worth pointing out that the SCSI standard is pretty successful at standardizing the hardware connection level (Apple excepted), but even with CCS (common command set) the software compatibility has a lot of problems. Sure the sequences for reading and writing are fairly uniform, but the sequences required required for "formatting" the drives, using bad block substitution, power up initialization vary widely. Also the values returned for reading capacity and geometry seem subject to random intrepretation. The general procdure for writing a SCSI driver is therefore to take a crack a writing a "generic SCSI" driver and then special case it until it works with each of the drives you feel your company is likely to use or that you have lying around and want to work. As a result, you can usually expect the same model drives, with the same or later ROM revision and hopefully their successors to work, but expect a new and random drive to work only somebody not only claims it works, but can demonstrate such from taking it from the box, formatting and using it. I suspect that once the "word" gets around about which drives do work and/or what tricks are required, the third party types will have lots of them. It takes a while. -- George Robbins - now working for, uucp: {uunet|pyramid|rutgers}!cbmvax!grr but no way officially representing arpa: cbmvax!grr@uunet.uu.net Commodore, Engineering Department fone: 215-431-9255 (only by moonlite)