[Soekris] PCI card + 5V kills board

Poul-Henning Kamp phk at phk.freebsd.dk
Mon Jul 7 14:56:47 UTC 2003

In message <20030707142617.GA31285 at cicely12.cicely.de>, Bernd Walter writes:
>I tried a Longshine USB2.0 card in a 4501 at 12V which seemed to work.
>Next I tried JP6 supply with GND at 1+2 and 5V at 3+4.
>The board died with a hearable tick :(
>After replacing the Q3 (the driver bridge for 3.3V regulator) the
>board worked again at 12V without additional cards.
>I retried 5V with the USB card which killed Q3 again.
>I have no clue if my 5V supplying was wrong or the USB2.0 card isn't
>really 3.3V aware - altough it has a 3.3V notch and claims to be
>PCI2.2 which implies 3.3V operating.
>My impression is that the card is just crap but I not happy to try
>out cards until it runs.
>Has anyone any expiriences to share?

There are two issues:  PCI signalling voltage (3.3 and 5.0) and 
PCI card power drain (3.3 and 5.0).

The PCI signalling can only be 3.3V, end of story.  That is what
the notches control.

The power drain is an entirely different story: both 3.3V and 5.0V
power is routed to the PCI card, but the 5.0V supply in the Soekris
has very little spare capacity so if the card drains too much power,
you have probably seen the result.

If you feed your Soekris with +5V, this is not an issue.

Poul-Henning Kamp       | UNIX since Zilog Zeus 3.20
phk at FreeBSD.ORG         | TCP/IP since RFC 956
FreeBSD committer       | BSD since 4.3-tahoe    
Never attribute to malice what can adequately be explained by incompetence.

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