Date: Wed, 20 Jul 2011 08:02:07 -0700 From: perryh@pluto.rain.com To: cswiger@mac.com, freebsd@jdc.parodius.com Cc: freebsd-stable@freebsd.org, peterjeremy@acm.org Subject: Re: Status of support for 4KB disk sectors Message-ID: <4e26edef.9op324NPX/MVOW1Y%perryh@pluto.rain.com> In-Reply-To: <84CC369B-4E70-414C-8C57-5FE772C7134F@mac.com> References: <CAN6yY1uaUqk2ifiNViJyMFJWf60a4DmCiVs3Z=--_TjtzseABQ@mail.gmail.com> <20110718234124.GA5626@icarus.home.lan> <CAN6yY1uaEwoEhEuoTNPqzywRaCPEvcLY-ddyFRUV00FcBDU1BA@mail.gmail.com> <E8F5CB22-21D5-4AF9-A690-1DB99D31F4CC@mac.com> <20110719211039.GA16085@server.vk2pj.dyndns.org> <02D367A5-CA74-4E8A-BE3E-F81485B287A7@mac.com> <4e26a250.iKKzhkOLoTB3sdOr%perryh@pluto.rain.com> <20110720031431.GA33758@icarus.home.lan> <84CC369B-4E70-414C-8C57-5FE772C7134F@mac.com>
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Jeremy Chadwick <freebsd@jdc.parodius.com> wrote: > On Wed, Jul 20, 2011 at 02:39:28AM -0700, perryh@pluto.rain.com wrote: > > IIRC, Plextor (and maybe some others) had a switch to select 512 or > > 2048 as the default transfer size, precisely so that they could be > > used as boot devices with systems that supported only 512. > > I don't think Plextor was around back then; they used to be called > TEXEL back in the early 90s. The only Sun SCSI CD drives I saw > were external and caddy-based, so I mentally correlate them with > NEC. Back then I wasn't looking at brands as much as I do today, > though. I still have a non-Sun 512-2048 drive; turns out it is a (caddy- based) Hitachi CDR-1750S rather than a Plextor. So much for remembering all the details from late in the Sun-3 era. (Plextor still rings a bell WRT the 512-2048 switch though; maybe some of the early Plextor drives also provided one.) Chuck Swiger <cswiger@mac.com> wrote: > Come to think of it, I do remember that switch, yes. > > Do you happen to know whether this limitation was part of the Sun > hardware, or of SunOS? CMU had a lot of Sun3 machines and NeXT > clusters, so I ended up mixing NeXT CD-ROM and the Canon? magneto- > optical drives with Sun H/W, and vice versa. Dunno if there were any hardware limitations, but most Sun-3 _bootroms_ predated CDROM support and thus could boot from a CD only by being fooled into believing it was a normal MFM or ESDI hard drive connected via an Adaptec ACB-4000 (SCSI-MFM) or Emulex MD21 (SCSI-ESDI) bridge controller. Remember those? This only worked if the CD drive's transfer size matched the expected hard drive sector size. I think the SunOS sr driver took the path of least resistance and issued an explicit "set transfer size 512" before trying to access the drive, thus enabling off-brand CD drives to work with the OS without running into any limitations that might have existed in either the hardware or the lower-level SCSI drivers, but that only worked after the OS had been booted :) > SunOS wasn't the only O/S which was run on a m68k Sun box. ;-) I'm aware of a NetBSD port that may still exist even today. Others?
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