SPI-2/Fast-40 pins

Jim McGrath jmcgrath at qntm.com
Tue May 23 10:57:44 PDT 1995


        Reply to:   RE>>SPI-2/Fast-40 pins

Why over 3 meters?   Single ended SCSI is defined for 6 m.  Fast SCSI
was restricted to 3, and Fast-20 to 1.5 to 3, but this was only for
data transfer operations - since we never changed anything having
to do with non-DATA phase operations, the original 6 m should still
hold.  If we enhance REQ/ACK/DATA/PARITY to go > 6 m, then 6 m 
due to the other lines beomes the limiting factor.

Actually, the original 6 m single ended SCSI limit was probably a
REQ/ACK type limit as well, so maybe we can go longer.  Does anyone
remember (John?) and/or have done empirical tests?

Jim


--------------------------------------
Date: 5/22/95 1:02 PM
To: Jim McGrath
From: Walter Bridgewater x2371
Received: by qm_smtpgw.qntm.com with SMTP;22 May 1995 13:02:11 U
Received: from worf.qntm.com (worf-gw.qntm.com) by mail.qntm.com with ESMTP
	(1.37.109.15/16.2) id AA168522361; Mon, 22 May 1995 12:52:42 -0700
Received: from mpdgw2.hmpd.com by worf.qntm.com with ESMTP
	(1.37.109.15/16.2) id AA203123018; Mon, 22 May 1995 13:03:38 -0700
Received: (from root at localhost) by mpdgw2.hmpd.com (8.6.8.1/8.6.6) id
OAA11795; Mon, 22 May 1995 14:02:35 -0600
Received: from aztec.ncrmicro.ncr.com(153.72.199.214) by mpdgw2.hmpd.com via
smap (V1.3)
	id sma011729; Mon May 22 14:01:41 1995
Received: from ncrwic.WichitaKS.NCR.COM (ncrwic.wichitaks.ncr.com
[153.79.8.1]) by Symbios.COM (8.6.8.1/8.6.6) with SMTP id OAA07619; Mon, 22
May 1995 14:00:49 -0600
Received: by ncrwic.WichitaKS.NCR.COM; 22 May 95 14:57:46 CDT
Received: by ncrcetc.WichitaKS.NCR.COM; 22 May 95 15:42:26 CDT
Received: by ncrhub4.ATTGIS.COM; 22 May 95 15:33:10 EDT
Received: by ncrgw1.ATTGIS.COM; 22 May 95 15:29:43 EDT
Received: from eng.adaptec.com ([162.62.20.6]) by milpitas.adaptec.com
(4.1/SMI-4.1)
	id AA05690; Mon, 22 May 95 12:22:24 PDT
Received: from atlantis by eng.adaptec.com (4.1/SMI-4.1)
	id AA19208; Mon, 22 May 95 12:20:59 PDT
Date: Mon, 22 May 95 12:20:59 PDT
From: wally at eng.adaptec.com (Walter Bridgewater x2371)
Message-Id: <9505221920.AA19208 at eng.adaptec.com>
To: scsi at wichitaks.ncr.com
Subject: RE: SPI-2/Fast-40 pins


SCSI Reflector,

I agree that at least ack, req, data & parity have to be differential
for the reasons Tak suggest.

If the other 7 signals are single ended, 
Then their slew rates should be slowed down proportional to any
length increase beyond 3 meters.

Regards,

Wally Bridgewater







More information about the T10 mailing list