From owner-freebsd-hackers Sat May 4 01:53:52 1996 Return-Path: owner-hackers Received: (from root@localhost) by freefall.freebsd.org (8.7.3/8.7.3) id BAA13112 for hackers-outgoing; Sat, 4 May 1996 01:53:52 -0700 (PDT) Received: from irz301.inf.tu-dresden.de (irz301.inf.tu-dresden.de [141.76.1.11]) by freefall.freebsd.org (8.7.3/8.7.3) with SMTP id BAA13097 for ; Sat, 4 May 1996 01:53:47 -0700 (PDT) Received: from sax.sax.de by irz301.inf.tu-dresden.de (8.6.12/8.6.12-s1) with ESMTP id KAA14248 for ; Sat, 4 May 1996 10:53:45 +0200 Received: by sax.sax.de (8.6.12/8.6.12-s1) with UUCP id KAA09545 for freebsd-hackers@freebsd.org; Sat, 4 May 1996 10:53:44 +0200 Received: (from j@localhost) by uriah.heep.sax.de (8.7.5/8.6.9) id KAA21347 for freebsd-hackers@freebsd.org; Sat, 4 May 1996 10:25:08 +0200 (MET DST) From: J Wunsch Message-Id: <199605040825.KAA21347@uriah.heep.sax.de> Subject: Re: using DLT drive on FreeBSD To: freebsd-hackers@freebsd.org (FreeBSD hackers) Date: Sat, 4 May 1996 10:25:08 +0200 (MET DST) Reply-To: joerg_wunsch@uriah.heep.sax.de (Joerg Wunsch) In-Reply-To: <199605031838.UAA01522@yedi.iaf.nl> from Wilko Bulte at "May 3, 96 08:38:54 pm" X-Phone: +49-351-2012 669 X-PGP-Fingerprint: DC 47 E6 E4 FF A6 E9 8F 93 21 E0 7D F9 12 D6 4E X-Mailer: ELM [version 2.4ME+ PL15 (25)] MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: owner-hackers@freebsd.org X-Loop: FreeBSD.org Precedence: bulk As Wilko Bulte wrote: > > 64 KB, this is enforced by physio(9) [man page not yet written :)]. > > Many SCSI adapters do only allow for 16 scatter/gather segments, and > > in the worst case, you need one of them for each physical page. > > This would imply that non-SG adapters are unusable. Correct me if I'm > wrong but something like a Seagate ST-02 (junk, I know, but sea(4) > is available) does not do SG. ...nor does it do busmaster DMA. :) Busmaster DMA controllers are required to support scatter/gather, that's why some early revision AHA-154X-A's are unusable with FreeBSD (but this was a firmware revision problem, mine is working fine in the scratchbox). -- cheers, J"org joerg_wunsch@uriah.heep.sax.de -- http://www.sax.de/~joerg/ -- NIC: JW11-RIPE Never trust an operating system you don't have sources for. ;-)