In a news article, we mentioned that eSATA could transfer data at 300Mbits/sec. I was wrong.
Bryan Kantack, a signal integrity expert with Agilent Technologies, Inc. in Colorado Springs, has pointed this out, e-mailing thus: "In your article, you refer to the new eSATA capability of 300Mbits/sec and compare that to 45Mbits/sec for USB high-speed."
"From my understanding of these specifications, I believe that the Serial ATA specification for external desktop applications (Gen2m or eSATA) provisions for 3.0Gb/sec data transmission per lane, which is 10-bit encoded for clock-recovery and line-balancing purposes."
"The 8-bit data recovered at the receiver would, therefore have a 20% reduction in data transfer rate due to 10b/8b conversion PLUS an 8:1 conversion from bits to bytes, allowing for 240MBytes/sec of actual data transfer."
"The 8b/10b conversion factor is smaller (10:8), but the differentiation between BYTES and BITS is fairly significant (8:1)." (I think Bryan may be being slightly ironic here.)
"Basically, this is just a technicality on nomenclature."
Bryan is right. A visit to Serial ATA web site corroborates his point.
Eg; "The typical cable length is 2 meters (6 feet); long enough to reach from a floor mounted PC to a drive placed on the desktop. The compliance is defined in the SATA II: Electrical Specification, as the Gen1m and Gen2m specifications for 1.5 Gb/s and 3.0 Gb/s respectively."
USB 2.0 offers up to 480Mbit/sec, meaning 80MB/sec. The Techworld article said USB 2.0 has "45Mbit/sec" which was quite wrong.
Thanks to Bryan for pointing this out.