Introduction

Unless you have been living under a rock, you will be no stranger to the Serial ATA standard that has become the new medium for mass storage connection to the PC. Serial ATA standards have now started to produce in mass on motherboards, with upwards of 4 ports standard on Intel, ULi, SIS and nVidia Southbridge's - not to mention the amount of additional controllers being added by motherboard makers, its not uncommon to see 6-8 SATA ports per motherboard.

Serial ATA's main claim to fame is serial transfer of data from the I/O logic to the HDD controller chips. Serialisation means using serial communication architecture, similar to that which was introduce by RAMBUS for its RDRAM memory. Serial ATA Generation 1 is able to transmit at a theoretical 1.5Gbps (or 150MB/s) between the Southbridge and the onboard system controller of the Hard Disk, however, limits in magnetic storage doesn't permit the HDD to actually take advantage of this - speed wise, SATA is no more faster than ATA-133 HDD's until NCQ come along.

NCQ or Native Command Queuing is fairly new to the Serial ATA standards. NCQ allows the HDD to smartly access data out of order rather than having to go though an order state to grab the required files, which can be located in different parts of the drive platers.

Another feature of Serial ATA is the reduced size of the cables while lengthening them at the same time. SATA cables are only 7 wires wide, as opposed to IDE which are 80 wires across. IDE also limits the size at just over 60cm long while Serial ATA can go up to 1 meter before a repeater is needed to power re-transmit data over longer cables.

Serial ATA Gen 1 did make some changes, now we have received Serial ATA Generation 2. SATA-II as it is known speeds the data transmission from 150MB/s up to 300MB/s between the HDD and the Southbridge chipset. nVidia and Intel are the first to offer this in their south bridges, with ULI, SiS and ATI soon to follow.

Today we are looking at the first SATA-II HDD to cross our labs, Western Digital's Caviar SE WD2500JS and comparing it to a high-performing Seagate SATA 7200.8 HDD.