Date: Thu, 21 Aug 1997 12:02:26 +0200 From: Andreas Klemm <andreas@wup.de> To: Stephen McKay <syssgm@dtir.qld.gov.au> Cc: freebsd-hardware@FreeBSD.ORG Subject: Re: Quiet SCSI disk? Message-ID: <19970821120226.20829@wup.de> In-Reply-To: <199708210918.TAA14147@troll.dtir.qld.gov.au>; from Stephen McKay on Thu, Aug 21, 1997 at 07:18:11PM %2B1000 References: <199708200348.NAA21476@ogre.dtir.qld.gov.au> <4472.872053261@time.cdrom.com> <19970820150743.09240@wup.de> <199708210918.TAA14147@troll.dtir.qld.gov.au>
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On Thu, Aug 21, 1997 at 07:18:11PM +1000, Stephen McKay wrote:
> On Wednesday, 20th August 1997, Andreas Klemm wrote:
>
> [about the 4GB DCAS 34330W]
>
> >Do you know how many tags it uses (tagged command queuing) ?
> >It was a bit disappointing for me, that the IBM DORS 32160 2.1GB
> >only offers 3 and the the famous QUEUE_FULL condistion ...
>
> I run mine off a Diamond FirePort 40 (uses the 53c875J chip). When I run
> ncrcontrol, it tells me it is using 4 tags. I don't know if I can use
> more. I remember reading somewhere that Stefan thinks 4 is a good number.
> I can't remember his reasoning, or where I read it. :-/
AHC driver uses normally 8 tags.
Or 4 if card doesn't have much SCM space.
And reduces the number of opennings to x, if a queue full race
condition occurs, where x = 3 using the IBM DORS... which is nearly
the same as running without tagged queuing ;-)
if ((inq_data->flags & SID_CmdQue)
&& !(ahc->tagenable & mask)) {
printf("%s: target %d Tagged Queuing Device\n",
ahc_name(ahc), xs->sc_link->target);
ahc->tagenable |= mask;
if (ahc->scb_data->maxhscbs >= 16
|| (ahc->flags & AHC_PAGESCBS)) {
/* Default to 8 tags */
xs->sc_link->opennings += 6;
} else {
/*
* Default to 4 tags on whimpy
* cards that don't have much SCB
* space and can't page. This prevents
* a single device from hogging all
* slots. We should really have a better
* way of providing fairness.
*/
xs->sc_link->opennings += 2;
}
--
Wiechers & Partner Datentechnik GmbH phone: +49 2173 3964 161
Support Unix - Andreas Klemm fax: +49 2173 3964 222
An der alten Ziegelei 2 mail1: andreas.klemm@wup.de
D-40789 Monheim mail2: andreas@FreeBSD.ORG
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