Date: Wed, 30 Apr 1997 12:30:07 +0930 (CST) From: Michael Smith <msmith@atrad.adelaide.edu.au> To: Don@PartsNow.com (Don Wilde) Cc: hackers@FreeBSD.ORG Subject: Re: 7860 Message-ID: <199704300300.MAA25127@genesis.atrad.adelaide.edu.au> In-Reply-To: <336621B0.545A@PartsNow.com> from Don Wilde at "Apr 29, 97 09:28:32 am"
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Don Wilde stands accused of saying: > Hi, Guys - > Could someone enlighten me as to what the problems are in the > Adaptec 7860 on-board 2940 chip are. Somebody referred to it as > 'brain-dead' in an earlier post. I have 2 of the Iwill/Quick Technology > boards running 2.1.7 and one which is a novell server with a 2940 board > added as a duplex controller. I have never had a problem with either of > the BSD systems (both of which are very lightly loaded at the moment), > but my Novell had a seizure for unknown reasons and I am wondering as to > the cause. > Can somebody enlighten me or point me to a web page with a > discussion of this? The range of Adaptec SCSI controllers of which the 7860 is a member use a data structure called an SCB for maintaining state about outstanding SCSI transactions. The 7880, the "original" chip on the 2940 card, can track 16 of these structures without requiring any help, allowing for up to 16 simultaneous SCSI transactions; a fairly comfortable number. The 7860 on the newer 2940's can only track three. There is support (the SCBPAGING option) for shuffling among these three to handle more simultaneous transactions, but obviously this requires more work on the part of the driver. Three transactions is less than the capacity of your average SCSI disk (4), and thus on anything other than a very quiet system is a nuisance at best. -- ]] Mike Smith, Software Engineer msmith@gsoft.com.au [[ ]] Genesis Software genesis@gsoft.com.au [[ ]] High-speed data acquisition and (GSM mobile) 0411-222-496 [[ ]] realtime instrument control. (ph) +61-8-8267-3493 [[ ]] Unix hardware collector. "Where are your PEZ?" The Tick [[
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