[1653] in linux-scsi channel archive
Re: SCSI Cables and aha2940
daemon@ATHENA.MIT.EDU (Chris Griffin)
Tue Apr 1 01:28:49 1997
Date: Tue, 1 Apr 1997 01:28:51 -0500 (EST)
From: Chris Griffin <boozer@vanadium.rollins.edu>
To: Andy Poling <andy@realbig.com>
cc: Dave Wreski <tel1dvw@is.ups.com>, "James T. Kirk" <root@plantel.com>,
linux-scsi@vger.rutgers.edu
In-Reply-To: <Pine.LNX.3.91.970331234650.28160X-100000@ws.realbig.com>
On Mon, 31 Mar 1997, Andy Poling wrote:
> On Mon, 31 Mar 1997, James T. Kirk wrote:
> > Well again it's probably a case of "It's not supposed to work"
> > when you put all connectors into use, it creates a fragmented SCSI chain,
> > with three terminations. SCSI is supposed to be a linear model with two
> > ends. Using all three make a fork in the chain and can result in echo and
> > other errors. Like I said, it's not supposed to work, and I wouldn't
> > trust it for real world data.
> >
> > Morgan Nelson
> > Plan Telecommunications
> >
> > On Mon, 31 Mar 1997, Dave Wreski wrote:
> >
> > >
> > > On Mon, 31 Mar 1997, James T. Kirk wrote:
> > > >
> > > > any two of the connectors may be used, but not all three. The way the
> > > > card is designed, using all three breaks SCSI termination rules and will
> > > > not work.
>
> The documentation that comes with the controller says explicitly not to use
> all three connectors. RTFM m'boy...
>
> As (ahem) Captain Kirk mentions, it is also contra the SCSI spec, which also
> expressly prohibits any `T' fitting of any sort - especially one as long as
> any cable would be.
>
> It's probably worth mentioning that using both the internal and external
> connectors (even in any legal combination of two) is likely to put you at
> risk of exceeding a legal length (which exact value escapes me at the
> moment). Especially with that long cable that Iomega supplies with the Jaz
> drive (in the grand tradition of suppliers of PC peripherals - "what, you
> have other peripherals too?!"). At the least, a Forced Perfect Termination
> terminator is advised...
>
> -Andy
>
> Global Auctions
>
Well, for some combinations it will and others it wont. If you are using
both wide connectors, the length limit is 6 meters or about 20 feet. IF
you use the fast internal connector, the length limit drops to 3 meters
(10 feet) and you probably will exceed the limit especially if you are
using the external wide connector, as every vendor I have delt with loves
those 6ft UW scsi cables (3 feet UW cables tend to cost MORE than 6 feet
UW cables!!!)
Chris
