4th RTL8139 card isn't working

Donald Becker becker@scyld.com
Thu Mar 9 09:08:28 2000

On Thu, 9 Mar 2000, Milan Hodoscek wrote:

> Donald> But that's not your problem.  Your problem is likely that
> Donald> the fourth slot is not a bus master slot.  The RTL8139 is
> Donald> a bus master and requires a bus-master-capable slot.
> While we are at it: Is it possible to share busmastering? Some (or all?)
> ABIT motherbords have tvo slots sharing busmastering, which means that
> RTL8139 drivers don't work if you put cards into both such slots.

Most common motherboard chipsets only support four sets of bus master wires.
That means motherboards with five PCI slots usually have one slot that's not
bus master capable.

I had thought that my ABIT BP6 motherboard had a slave-only slot (typically
it's the shared PCI/ISA slot), but you are correct that it actually shares
the bus master control signals with the adjacent slot.  This was likely done
to conform to PCI v2.0/v2.1, which specifies that all PCI slots must now be
bus master capable.

So putting two bus master cards in the shared slots is a "user error",
because this limitation listed in the manual.  But few would be able to
guess this limitation without carefully reading the manual, especially since
all slots work with bus master cards individually.

Donald Becker
Scyld Computing Corporation, becker@scyld.com

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