Date: Thu, 31 Aug 1995 17:34:16 -0700 From: "Justin T. Gibbs" <gibbs@freefall.FreeBSD.org> To: "Rodney W. Grimes" <rgrimes@gndrsh.aac.dev.com> Cc: FreeBSD-hackers@freebsd.org Subject: Re: 4GB Drives Message-ID: <199509010034.RAA03131@freefall.FreeBSD.org> In-Reply-To: Your message of "Thu, 31 Aug 95 17:18:37 PDT." <199509010018.RAA13189@gndrsh.aac.dev.com>
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>> 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
===========================================
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