From owner-freebsd-hackers Thu Aug 31 17:34:18 1995 Return-Path: hackers-owner Received: (from majordom@localhost) by freefall.FreeBSD.org (8.6.11/8.6.6) id RAA03140 for hackers-outgoing; Thu, 31 Aug 1995 17:34:18 -0700 Received: from localhost (localhost [127.0.0.1]) by freefall.FreeBSD.org (8.6.11/8.6.6) with SMTP id RAA03131 ; Thu, 31 Aug 1995 17:34:16 -0700 Message-Id: <199509010034.RAA03131@freefall.FreeBSD.org> X-Authentication-Warning: freefall.FreeBSD.org: Host localhost didn't use HELO protocol To: "Rodney W. Grimes" cc: FreeBSD-hackers@freebsd.org Subject: Re: 4GB Drives In-reply-to: Your message of "Thu, 31 Aug 95 17:18:37 PDT." <199509010018.RAA13189@gndrsh.aac.dev.com> Date: Thu, 31 Aug 1995 17:34:16 -0700 From: "Justin T. Gibbs" Sender: hackers-owner@freebsd.org Precedence: bulk >> One thing to watch out for is that even without tagged queuing, you >> can get up to two requests per target sitting on the board. You'll > >Those are the 2 I need to eliminate for my analysis. Any quick dirty >hack I can do to turn them off? Then set the number of commands that the scsi system is allowed to queue to 1 instead of 2. Look on line 882 of aic7xxx.c: ahc->sc_link.opennings = 2; Should be changed to 1. >> have to blink something when the command that gets taken off the queue >> is for a target that has an active command pending since it will re-queue >> the transaction in that case. This will happen when the first transaction >> to the disk disconnects to do the seek. > >Test case has already eliminated all seeks. Seeks do not occur as my total >transfer is smaller than 1 cylinder * stripe width. I am trying to find >the proper parameters and emperical data to improve my theoritcal caclulations >and formulas. I can't find the errors in these algorithms without some >correlation to real measured data to find the bad assumptions in them :-(. Hmm. Are you sure that the drive will not disconnect even for a short time after receiving its command? >The data I need is being very difficult to obtain without spending major >dollars on a scsi bus analyzer and a large logic analyzer :-(. I guess >I could go out to the labs some weekend, but it is a pain to check in this >much equipment. I would think that a scope attached to the led line would be sufficient for most of the timing. >-- >Rod Grimes rgrimes@gndrsh.aac.dev.com >Accurate Automation Company Reliable computers for FreeBSD -- Justin T. Gibbs =========================================== Software Developer - Walnut Creek CDROM FreeBSD: Turning PCs into workstations ===========================================