(Some quick crib notes for those of you who haven't been following along / aren't total geeks: I recently rebuilt ph34r, the FreeBSD server in my home office, with an Athlon 64 3000+. Unlike in Windows, where you would have to operate that chip in 32-bit mode - the same as a regular Athlon or a Pentium - under FreeBSD, you can operate it in its native 64-bit mode. SSH is a way of pulling up a shell - think of it like a DOS window - on a remote computer over the network, but your network traffic to and from that remote computer is heavily encrypted for security reasons. You can also use an SSH "tunnel" to transfer other data, like copying files, which is what I did in the tests below.)
The test I set up was as follows: create a RAMdisk, put a 150MB file in it, then copy the file from the RAMdisk through an SSH tunnel to localhost:/dev/null. My "control" machines were an Athlon 2600+ with 1GB of PC3200 memory running FreeBSD 4.10, an Athlon 2400+ with 1GB of PC3200 memory running FreeBSD 5.1, and the "test" machine was ph34r, an AMD64-mode Athlon 64 3000+ with 1GB of PC3200 memory running FreeBSD 5.2.1.
The throughput results came out as follows:
Athlon 2600+: 8.1 MB/sec
Athlon 2400+: 8.0 MB/sec
Athlon64 3000+: 16.3MB/sec
It's worth noting that the true clock speeds on those machines are 2.0 GHz (Athlon 2400), 1.9GHz (Athlon 2600), and 2.0 GHz (Athlon64 3000+). So the Athlon64 in AMD64 mode was actually hammering out better than double the SSH throughput of machines running at the same clock speed. Damn. =)