[Fwd: U160/m Waveforms.]

John Lohmeyer lohmeyer at ix.netcom.com
Wed Feb 17 09:52:23 PST 1999

* From the T10 Reflector (t10 at symbios.com), posted by:
* John Lohmeyer <lohmeyer at ix.netcom.com>

I added the text as the first page of the PDF file and have posted it on
the T10 ftp/web site as 99-131r0.pdf.  The URL is:



cc: T10 Reflector

At 2/16/99 04:33 PM, you wrote:
>Attached is what I tried to put on the reflector. The text should appear
>with the attachment that shows the signals. Hopefully you can put this
>Vince Bastiani
>Message-ID: <36BB980A.A8C0CEF8 at corp.adaptec.com>
>Date: Fri, 05 Feb 1999 17:17:00 -0800
>From: Vince Bastiani <bastiani at corp.adaptec.com>
>X-Mailer: Mozilla 4.04 [en] (WinNT; U)
>MIME-Version: 1.0
>To: t10 at symbios.com
>CC: Tariq Abou-Jeyab <tajeyab at corp.adaptec.com>
>Subject: U160/m Waveforms.
>Content-Type: multipart/mixed;
>Content-Type: text/plain; charset=iso-8859-1
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ixmail7.ix.netcom.com id QAA29701
>- Capacitive Loads vs. Real Drives.
>In the T10 meeting held Jan. 26, we presented setup and hold time
>measurements for U160/m SCSI. Several configurations were used including
>12 m, 32 AWG, MQT multi-drop cable and 1.5 m, 30 AWG, fully-laminated
>twist ‘n flat multi-drop cable. We used a U160/m Adaptec host adapter
>and a U160/m Quantum hard drive and the rest of the loads were just pure
>capacitive loads, with 15 pF to ground on each of +/- lines.
>Several people commented about the use of capacitive loads to simulate
>drives, they felt drives were not totally capacitive. Hence, we decided
>to run additional testing while placing the drive at two different
>positions; at the end of the cable near the terminator and at the first
>load position. This shows using capacitive loads in place of  drives is
>a good approximation when viewing loading effects on setup and hold
>measurements, and signal quality.
>The attached waveforms show the short cable test. We did write
>operations and viewed the signals as they passed by various load
>position. We looked at several positions along the two cables with the
>drive either the first device or the last on the bus. The waveshapes
>show similar traces whether the signal passed by the drive first or
>passed by all the capacitive loads before getting to the drive. The
>reflections seem more severe when the drive is positioned at the end.
>This would indicate the drive is not pure capacitive but has some
>resistive nature to it which smoothes the reflective pulses when
>positioned first, but does not severely impact the amplitude of the
>signal for this minimum loaded short cable.
>We intend to do some further testing with more drives and longer cables.
John Lohmeyer                  Email: lohmeyer at ix.netcom.com
LSI Logic Corp.                Voice: +1-719-533-7560
4420 ArrowsWest Dr.              Fax: +1-719-533-7036
Colo Spgs, CO 80907              BBS: +1-719-533-7950

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