[U-Boot-Users] IceCube MPC5200 PCI crash - need help

Wolfgang Denk wd at denx.de
Wed Nov 30 15:35:21 CET 2005

In message <47F3F98010FF784EBEE6526EAAB078D1C05EE4 at tq-mailsrv.tq-net.de> you wrote:
> According to the PCI specification this _should_ work. But there
> are PCI cards around with a 5 V key and a 3,3 V key (=3D combo-cards)
> wich drive 5 V on the PCI signals. Those cards are not compliant to
> the PCI spec, and could damage a 3,3 V only PCI board.

Well, but that's a problem with  any  hardware:  using  non-compliant
cards may cause damages.

> On the IceCube board the signal levels on the PCI bus must not exceed
> 3,3 V, because the PCI pins of the MPC5200 are not 5 V tolerant. So 
> it must be assured that a 3,3 V/5 V combo-card drives the PCI pins only
> with 3,3 V. Otherwis it _may_ work for a while (because the 5 V are 
> shortend by the clamp diodes in the MPC5200 down to 3,3 V), but damage
> the board sooner or later.

Usually (i. e. in all cases I've seen so far - and yes, it  was  more
than one :-( ) the SDRAM will die, and immediately.

Best regards,

Wolfgang Denk

Software Engineering:  Embedded and Realtime Systems,  Embedded Linux
Phone: (+49)-8142-66989-10 Fax: (+49)-8142-66989-80 Email: wd at denx.de
No, I'm not going to explain it. If you  can't  figure  it  out,  you
didn't want to know anyway... :-)
                   - Larry Wall in <1991Aug7.180856.2854 at netlabs.com>

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