Intel PRO/1000CT Gigabit ethernet with CSA (fwd)

Donald Becker becker at
Fri Jun 27 20:57:34 EDT 2003

On Fri, 27 Jun 2003, Mark Hahn wrote:

> Hi Don.  do you happen to have any experience 
> with this new CSA feature - specifically whether it 
> actually lowers gigabit latency?

This appears to connect directly to the internal motherboard chipset
crossbar, giving high-bandwidth access without (directly) conflicting
with the PCI bus.

This architecture does reduce the bus access latency compared PCI, but
there will be no measurable reduction in network communication latency.

If there were a Infiniband adapter connected to the same crossbar port,
you *would* be able to notice a significant reduction in single-word
transfer latency.

> Streaming Architecture) bus ? The Intel fact sheet is, as often, short
> on quantitative detail but it looks promising:

Yup, this is very similar to the way earlier Intel Fast Ethernet chips
connected to the Intel chipsets.  If you look at the motherboards you'll
see that those chips had significantly fewer pins than the PCI NICS, yet
they appear to software to be a regular PCI device.

> How does this NIC and a switch compare to Myrinet and similar
> networks?

Almost exactly the same as a 66Mhz PCI adapter.

> modern 24 port switch like the Dell PowerConnect 5224, leading to
> dropped packages and crashing jobs.

You'll have the same constraints:
   Don't saturate with small packets
   Minimize multicast and broadcast packets
      Limit to low-rate service establishment (i.e. not back-to-back)
      Don't use for data transport.

Donald Becker				becker at
Scyld Computing Corporation
914 Bay Ridge Road, Suite 220		Scyld Beowulf cluster system
Annapolis MD 21403			410-990-9993

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