Take a PC from fifteen years ago and one from this year, and rip open the lids. Look inside. Very little is similar: memory chips have leaped off the motherboard and onto tiny SIMMs, the processor is no longer long and black but hides beneath a turbo-assisted futurist heatsink, and the masses of support chips have congealed into one or two postage stamps. One thing remains unchanged -- the fat, flat ribbon cables that hook the hard disks to the motherboard. The signals in those cables aren't that different either. The original IBM AT hard disk interface ran a protocol called ATA -- AT Attachment -- which after a while also became known as IDE, Integrated Device Electronics. There have been numerous variations for speed and commercial reasons, including the still-developing ATA/ATAPI (ATA with Packet Interface) 6, but the basic format of the bus remains: lots of 5v signals rushing around in parallel. ATA/ATAPI 6 specifies up to eighty conductors in the cable. Which is all very 90s. These days, computer circuitry prefers to run at between 1 and 3 volts -- the lower the better -- and in as small as space as possible. They also run hot, and big flat cables get in the way of airflow. As a result, an industry consortium has been preparing Serial ATA; same commands, same data transfer protocol but done over a six-core cable roughly the diameter of a CD-ROM audio lead, with signals swinging through half a volt one bit at a time. Although that might sound inherently slower, the bit speed is up at 15 gigabits/second (Gb/s), which translates to 150 megabytes/second (MB/s). That's faster than the 100 MB/s of the ATA/100 standard currently propping up most fast desktops, and lots faster than hard disks currently deliver. It's not quite as fast as the top-rated variant of SCSI, the other common disk interface standard -- Ultra160 SCSI runs at 160 MB/s -- and it's head to head against ATA/133 but it should pan out a lot cheaper than either.. Over the next ten years of Serial ATA's planned lifetime, the speed is expected to rise to around 600 MB/s to keep pace with storage capabilities. Speed, low voltage operation and thin cabling aren't the only advantages. Serial ATA requires no changes to existing operating systems and BIOS support, so it'll be easy to add to existing systems. Also, unlike ATA it's hot-pluggable: you can add and remove disks to the system while power is applied and software is running. That makes it usable for RAID storage, where multiple hard disks run copies of the same data simultaneously for higher reliability: when one goes down you can replace it without stopping the system.