Date: Wed, 30 Sep 1998 23:20:33 +0100 (BST) From: Andrew Gordon <arg@arg1.demon.co.uk> To: Karl Denninger <karl@Denninger.Net> Cc: current@FreeBSD.ORG Subject: Long SCSI probes (was Re: Long IDE probes?) Message-ID: <Pine.BSF.3.96.980930231258.20359B-100000@server.arg.sj.co.uk> In-Reply-To: <19980930113836.A4061@Denninger.Net>
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On Wed, 30 Sep 1998, Karl Denninger wrote: > > What I don't understand is the reason for the long probes (that is, more > than a second or two) in any of the disk devices. > > IDE by definition is probed by the BIOS before boot. Either the disk is > there or it is not, and you don't get out of POST and to Boot until that's > determined. Therefore, a long wait there is COMPLETELY pointless. > > SCSI devices similarly are probed by the adapter BIOS. Again, there is no > reason for the long wait that I can fathom. Note that the SCSI bus is reset before probing; SCSI devices vary wildly in their reaction to this. I have a tape drive that, if there is a tape in the slot, engages in considerable tape movement (presumably to detect the tape format/capacity) - this device requires (pre-CAM) SCSI_DELAY=23 to survive rebooting with a tape loaded. Even disc drives vary from near-instantaneous to several seconds response time. To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-current" in the body of the message
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