[3c509] On chip ram of 3c905C

Donald Becker becker@scyld.com
Mon Feb 18 14:28:01 2002

On Sun, 17 Feb 2002, Kallol Biswas wrote:

> To: 3c509@scyld.com
> Subject: [3c509] On chip ram of 3c905C

Note that this is the 3c509 (ISA) mailing list.  The proper list for the
3c905 (PCI) is the 'vortex' list.

>    Has any one used the onchip ram of 3c905C family
> of cards for RX descriptor ring or TX descriptor ring?
> Or am I misunderstanding something?

The on-chip RAM is used as the FIFO buffer.  It is not mapped into the
memory space of the host, and therefore cannot be used as the descriptor

Even if you could map the memory, it would be a horrible idea.
The whole point of a descriptor-based architecture is that the NIC does
the time consuming work of reading and writing the packets to main
memory, where the CPU can access it at full speed.

Donald Becker				becker@scyld.com
Scyld Computing Corporation		http://www.scyld.com
410 Severn Ave. Suite 210		Second Generation Beowulf Clusters
Annapolis MD 21403			410-990-9993