PIO NICs.

Donald Becker becker at scyld.com
Mon Oct 15 11:43:13 EDT 2001


On Mon, 15 Oct 2001, Hong Ong wrote:

>   currently, I am trying to compile a list of NICs that support 
> programed I/O (PIO). However, I only manage to find one which is
> Myrinet.

Very few modern Ethernet NICs support programmed I/O.

PIO is faster for tiny packets, but adds too much CPU overhead for
Ethernet-sized packets.  So you are likely to see PIO only for
cluster network adapters, not Ethernet.

The only PCI Ethernet adapters that support PIO are the NE2000 clones,
usually 10Mbps only, and the 3Com 3c590/3c900 series boards.  A few of
the current 3Com designs still have the legacy PIO support, but it's
rarely used and never tested.

There are a few other chips where it's possible to use the FIFO
diagnostic capability to send PIO packets, but not operationally.  There
are too many hardware races.

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


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