Subject: Re: Hardware checksums slow down max throughput on ti(4) board?
To: Jeff Rizzo <>
From: Jason R Thorpe <>
List: current-users
Date: 12/17/2001 12:12:19
On Mon, Dec 17, 2001 at 11:49:38AM -0800, Jeff Rizzo wrote:

 > Using ttcp for some basic throughput testing, I find that without
 > hardware checksumming (ip4csum, etc) enabled, I can get a max
 > throughput of about 280Mbps on a TCP connection, and close to
 > 800Mbps for raw UDP (with drops).  *With* hardware checksums enabled,
 > max throughput is about 227Mbps for a TCP connection, and 175Mbps for
 > raw UDP. (!)

This is a known bug in the Tigon-1 Gig-E chip.  The Tigon-1 doesn't
have the horsepower to do normal Gig-E stuff + checksumming (it's a
MIPS R4000 core).  The Tigon-2 has 2 cores in the chip, which made up
for a lot of it.

Plus, the stock Alteon firmware is known to suck in a lot of ways; SGI,
in their driver for that chip, heavily hacked the firmware to make it
not suck.

        -- Jason R. Thorpe <>