From owner-freebsd-stable@FreeBSD.ORG Wed Jul 20 08:22:06 2011 Return-Path: Delivered-To: freebsd-stable@freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2001:4f8:fff6::34]) by hub.freebsd.org (Postfix) with ESMTP id 3225E106566B for ; Wed, 20 Jul 2011 08:22:06 +0000 (UTC) (envelope-from perryh@pluto.rain.com) Received: from agora.rdrop.com (agora.rdrop.com [IPv6:2607:f678:1010::34]) by mx1.freebsd.org (Postfix) with ESMTP id 0B8568FC08 for ; Wed, 20 Jul 2011 08:22:06 +0000 (UTC) Received: from agora.rdrop.com (66@localhost [127.0.0.1]) by agora.rdrop.com (8.13.1/8.12.7) with ESMTP id p6K8M2LG089396 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-SHA bits=256 verify=NOT); Wed, 20 Jul 2011 01:22:03 -0700 (PDT) (envelope-from perryh@pluto.rain.com) Received: (from uucp@localhost) by agora.rdrop.com (8.13.1/8.12.9/Submit) with UUCP id p6K8M2aF089395; Wed, 20 Jul 2011 01:22:02 -0700 (PDT) Received: from fbsd81 ([192.168.200.81]) by pluto.rain.com (4.1/SMI-4.1-pluto-M2060407) id AA18536; Wed, 20 Jul 11 01:01:44 PDT Date: Wed, 20 Jul 2011 08:02:07 -0700 From: perryh@pluto.rain.com To: cswiger@mac.com, freebsd@jdc.parodius.com Message-Id: <4e26edef.9op324NPX/MVOW1Y%perryh@pluto.rain.com> References: <20110718234124.GA5626@icarus.home.lan> <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> In-Reply-To: <84CC369B-4E70-414C-8C57-5FE772C7134F@mac.com> User-Agent: nail 11.25 7/29/05 Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: 7bit Cc: freebsd-stable@freebsd.org, peterjeremy@acm.org Subject: Re: Status of support for 4KB disk sectors X-BeenThere: freebsd-stable@freebsd.org X-Mailman-Version: 2.1.5 Precedence: list List-Id: Production branch of FreeBSD source code List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Wed, 20 Jul 2011 08:22:06 -0000 Jeremy Chadwick 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 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?