Date: Sun, 16 Jul 1995 12:16:10 -0500 (CDT) From: "Karl Denninger, MCSNet" <karl@mcs.com> To: freebsd-hackers@freebsd.org Subject: Twinchannel SCSI Adapter change Message-ID: <m0sXXIY-0003kwC@mercury.mcs.com>
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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!
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