re: about 21554 bridge

[Alan Deikman <Alan.Deikman@znyx.com>]

>From: sun zhi-gang <zgsun@nudt.edu.cn>

>Everyone:
>    My project is a SMP structure, six cpu boards are connected by
>CompactPCI
>backplane. I know intel's 21554 can be used as PCI-to-PCI bridge. My
>question
>is :
>    if one board is slave, 21554's primary inteface must face the
>backplane, i don't
>know if one board is master, which interface should face the backplane,
>primary
>or secondary?
>thanks a lot.

I would say that you would connect the PRIMARY bus side 
of the 21554 to the backplane, and the SECONDARY bus side
has the CPU on it.  There are several reasons for this,
and these are based on the concept that from the 21554's
point of view your CPU will be an embedded controller.
This is what the chip was designed for.  You can "set
up" the 21554 from the secondary time at power-on or
reset from software running on the secondary side,
not the primary side.

More importantly, the HotSwap support is on the PRIMARY
side.  You didn't mention if you wanted hot swappability,
but of course you do ;) being an engineer.

If I were doing this, I would try to make this work
with only one type of plug-in board -- no difference
between "master" and "slave."  The difference would be
between the slots on the backplane.  

Good luck, this looks like a fun project.

-----------------------
  Alan.Deikman@znyx.com