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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