Re: [SI-LIST] : PCI length calculations

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From: Suchitha.V@smartm.com
Date: Thu Feb 22 2001 - 12:34:23 PST


        Hello Scott,

        Thankyou for your eply.

        Could you please desribe the possible resonance conditions that
occur on a PCI bus?
        You mentioned that short PCI busses that do not work over all
posssible conditions also exist.
        Could you please mention some of these conditions?

        For example, my mother board has two 64-bit PCI slots connected to
Intel's 21154.
        I find the following problems.

        1) When gigabit ethernet cards (from Netgear) are inserted in these
slots, FTP operations at temperatures below 8 degree centigrade
             causes the system to lock up. The system runs on Windows NT
server, service pack 6.0.
        2) Sometimes the system locks up after loading drivers for the
Netgear gigabit ethernet cards.

        I would like to know where to probe.

        Looking forward to your reply.

        Regards
        suchitha

        From: Scott McMorrow@scott on 02/21/2001 01:03 PM
        To: Suchitha V/Apex Data Inc/01@Apex Data Inc
        cc: si-list@si-list@silab.eng.sun.com@SMTP@EXCHANGE,
bpatel@bpatel@cyras.com@SMTP@EXCHANGE

        Subject: Re: [SI-LIST] : PCI length calculations

        Suchitha,

        Because the PCI is a reflected wave bus with non-uniform
        stubs, there is no closed form analytical way to determine the
maximum
        trace length for reliable operation. There are too many possible
        resonance conditions that may occur.

        The only way to guarantee reliable PCI bus operation is thorough
        rigorous simulation and sensitivity analysis of the devices, board
        conditions and parametric variations.

        I can guarantee you that there are many short PCI busses which
        do not work over all possible conditions, and many long PCI busses
        which do. The difference is good design and system simulation.

        regards,

        scott

        --
        Scott McMorrow
        Principal Engineer
        SiQual, Signal Quality Engineering
        18735 SW Boones Ferry Road
        Tualatin, OR 97062-3090
        (503) 885-1231
        http://www.siqual.com

        Suchitha.V@smartm.com wrote:

> Hi,
>
> I have 8 devices on the PCI bus. This is for custom mother board
> application.
>
> Regards
> suchitha
>
> Hi! Can you mentions how many devices are on this PCI bus and
whether this
> PCI is being implemented for motherboard or using chips with PCI
compliant
> interface on a single board?
> Bhavesh
>
> -----Original Message-----
> From: Suchitha.V@smartm.com
> To: si-list@silab.eng.sun.com
> Sent: 2/20/01 8:55 PM
> Subject: [SI-LIST] : PCI length calculations
>
> Hello All,
>
> I have a question regarding PCI length calculations for a 32 bit
33 MHz
> PCI
> Bus.
> How do you arrive at the maximum length for a PCI 33 MHz bus?
> I have done some calculations to arrive at the routed length
required.
> But the length is much lesser than the PCI length specified for
33MHz(
> which
> assumes say 12 inches as maximum)
> Can anyone explain how to arrive at PCI lengths
>
> Looking forward to your replies and suggestions
>
> Regards
> Suchitha
> ?
>
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