Date: Mon, 17 Jul 1995 17:08:47 -0500 (CDT) From: Karl Denninger <karl@Mcs.Net> To: julian@ref.tfs.com (Julian Elischer) Cc: karl@mcs.com, freebsd-hackers@freebsd.org Subject: Re: Twinchannel SCSI Adapter change Message-ID: <199507172208.RAA02711@Jupiter.mcs.net> In-Reply-To: <199507171716.KAA11374@ref.tfs.com> from "Julian Elischer" at Jul 17, 95 10:16:10 am
next in thread | previous in thread | raw e-mail | index | archive | help
> > You really need to probe them in the same order as DOS (the BIOS) does, > or you may not be able to get to your root disk and boot from it as well.. > (the C:->sd0 > D:->sd1 > -- > E:->sd2 > mapping would become > C:->sd1 > D:->sd2 > -- > E:->sd0 > > > and I'm pretty sure we couldn't boot from that :) > The boot/kernel translation needs a LOT of work.. If the kernel read the EISA config, this would be possible. But it doesn't, and thus isn't. -- Karl > > Good afternoon, > > > > I have changed the probe order on the twin channel SCSI 2742 adapter here to > > probe "b" first. > > > > The reason is this: > > > > 1) "A" has both internal and external connectors. > > 2) "B" has only an internal connector. > > > > You probably will want to boot from an internal disk drive, or if you do > > not, you probably want to have ALL disks external. > > > > If you boot from an internal disk, there is no reason not to use it on > > channel "B". > > > > If you have an internal and external disk setup, why not boot from "B" and > > have your externals on the only available connector -- "A"? This reduces > > adapter contention and improves performance. > > > > If the device is a single-channel one, we do not probe "B". > > > > If there are no disks on "b", then probing it is harmless. > > > > If the boot disk is on "B", it gets sd0() so that root mounts correctly, and > > your other devices on the external bus are not affected. > > > > This also solves impedence problems I've seen on Adaptec boards which come > > up if you try to use both internal and external cabling on the same disk > > channel. I recommend AGAINST doing this for that reason if at all possible. > > > > Anyone want these changes (move two lines) for the production code base, or > > does anyone else think this is a good (or bad) idea? > > > > -- > > -- > > Karl Denninger (karl@MCS.Net)| MCSNet - The Finest Internet Connectivity > > Modem: [+1 312 248-0900] | (shell, PPP, SLIP, leased) in Chicagoland > > Voice: [+1 312 248-8649] | 7 Chicagoland POPs, ISDN, 28.8, much more > > Fax: [+1 312 248-9865] | Email to "info@mcs.net" WWW: http://www.mcs.net > > ISDN - Get it here TODAY! | Home of Chicago's only FULL AP Clarinet feed! > > > >
Want to link to this message? Use this URL: <https://mail-archive.FreeBSD.org/cgi/mid.cgi?199507172208.RAA02711>