Date: Sun, 11 Mar 2001 23:45:40 -0500 From: George Morgan <gemorga2@vt.edu> To: Matthew Jacob <mjacob@feral.com> Cc: freebsd-scsi@FreeBSD.ORG Subject: Re: SCSI speed with SLR100 tape drive Message-ID: <3AAC0E24.30330.73F53E@localhost> In-Reply-To: <Pine.BSF.4.21.0103112024370.52110-100000@beppo.feral.com> References: <200103120325.KAA09448@banyan.cs.ait.ac.th>
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Hmm, according to the Tandberg website, the SLR100 supports up to Ultra2-Wide SCSI which from what I understand, the Ultra2 narrow bus supports 40 MB/sec max transfer rate and the Ultra2 wide bus supports 80 MB/sec max transfer rate. The probe message suggests that the bus is running at 20 MHz with 16 bits per transfer (wide SCSI) which should mean an effective data rate of 40 MB/sec as listed in the message. To achieve the manufacturer specified Ultra2 performance the bus would have to use a 40 MHz clock rate, unless data is transferred on the rising and falling edges of the clock. According to what I was able to find on the web about SCSI specifications, transfers on the rising and falling edges of the clock are not used until you get to Ultra3/Ultra160 or Ultra320 which this drive does not appear to support. Of course I could be totally wrong since I am not a SCSI expert. Please clarify or provide a URL to an explanation that fits your claims. Thanks. > On Mon, 12 Mar 2001, Olivier Nicole wrote: > > > > > Hello, > > > > I finally got that SLR100 tape drive I wanted. It si supposed to > > support SCSI 160, but anyway the machine I have only supports 80Mb. > > > > The problem is the following: > > > > - at boot time, going to the Symbios bios, the tape is given at > > maximum speed, 80 Mb > > > > - once FreeBSD is started, it only supports half the speed: > > sa0 at sym1 bus 0 target 2 lun 0 > > sa0: <TANDBERG SLR100 0402> Removable Sequential Access SCSI-2 > > device sa0: 40.000MB/s transfers (20.000MHz, offset 15, 16bit) > > > > Any idea on the reason why? > > It's not 'half the speed'. Please go read some SCSI FAQs somewhere. > > > > > Eventually, I had to modify /usr/src/sys/cam/scsi/scsi_sa.c to > > remove the leading blank from the model name in the quirk table. > > > > > > Best regards, > > > > Olivier > > > > To Unsubscribe: send mail to majordomo@FreeBSD.org > > with "unsubscribe freebsd-scsi" in the body of the message > > > > > To Unsubscribe: send mail to majordomo@FreeBSD.org > with "unsubscribe freebsd-scsi" in the body of the message George Morgan Virginia Tech Electrical Engineering Class of 2000 (Graduating May 2001 as a Co-op) To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-scsi" in the body of the message
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