[SI-LIST] Re: ADDITIONAL PCI CLOCKS
- From: "Moran, Brian P" <brian.p.moran@xxxxxxxxx>
- To: "'si-list@xxxxxxxxxxxxx'" <si-list@xxxxxxxxxxxxx>
- Date: Fri, 13 Jul 2001 16:34:29 -0700
If you go with the split at the source series terminated approach, rather
than spliting after the series termination resistor, you would be better off
using two separate series resistors, with each one matched correctly. This
way there is some isolation between the two branches to prevent the end line
reflections from bouncing back and forth between the two loads.
Brian P. Moran
Signal Integrity Engineer
Intel Corporation
brian.p.moran@xxxxxxxxx
-----Original Message-----
From: S. Weir [mailto:weirsp@xxxxxxxxxx]
Sent: Friday, July 13, 2001 2:56 PM
To: si-list@xxxxxxxxxxxxx
Subject: [SI-LIST] Re: ADDITIONAL PCI CLOCKS
Frank,
I would vote for using one driver to two loads that are close enough to
each other that the stub will not introduce a substantial step, and are
part of the main board.
Regards,
Steve.
At 03:37 PM 7/13/01 -0700, you wrote:
>Why not drop the resistor and make the two branching traces 2x the line's?
>
>Frank Paglia
>
>-----Original Message-----
>From: Ingraham, Andrew [mailto:Andrew.Ingraham@xxxxxxxxxx]
>Sent: Friday, July 13, 2001 2:50 PM
>To: 'si-list@xxxxxxxxxxxxx'
>Subject: [SI-LIST] Re: ADDITIONAL PCI CLOCKS
>
>
>
> > I thought of using one of the PCI outputs of the
> > synthesizer to drive two PCI devices as follows:
> > The output will be given to a resistor (value equals
> > half the line's characteristic impedance minus the
> > driver's source impedance). The other end of this
> > resistor will then be split into two traces that are
> > routed to the individual PCI devices.
>...
> > Is there
> > something I ought to care of?
>
>Don't forget to check what happens when one of those PCI load devices isn't
>there (PCI card not plugged in). Or make sure that those outputs don't go
>to plug-in cards.
>
>Instead of one resistor with half the resistance, you could use two
>resistors of (about) the same resistance as the others, thus giving you
some
>isolation between the two clocks.
>
>Andy
>
>
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