Posted on Wed 14 April 2021

advanced technology

Fun fact of the day: the AT in SATA is a direct reference to the IBM PC/AT launched in 1984.

Let’s work backwards.

SATA, the Serial AT Attachment, is different from PATA, the Parallel AT Attachment because, among other things, it uses a 7 conductor cable rather than a 40 or 80 conductor cable. The accompanying power connector is wider than the standard data cable.

PATA was formerly ATA, back when it didn’t have a serial competitor. It was also called EIDE, Enhanced Integrated Drive Electronics, and before that just Integrated Drive Electronics. All of these names stem from the fact that the connector just extends the PC/AT 16 bit ISA bus out to the drive, where the controller is mounted on the drive itself.

Prior to ATA, drives had dedicated controllers that plugged into the system bus, that then ran cables out to the disk drive itself. Some controllers could handle two disks!

If you had a fancy computer, you might have had a Small Computer Systems Interface controller, SCSI. That could talk to 7 other devices in its original incarnation. SCSI controllers were expensive and SCSI disks were expensive, but SCSI could also talk to printers and scanners and similar strange beasts. The SCSI protocol lives on in SAS, Serial Attached SCSI – which uses the same connectors as SATA. Almost all SAS controllers can talk to SATA disks, so having the SAS capability is useful.

The original ATA spec could transfer 8.3MB/s. SATA3 specifies 6GB/s. The latest successor, U.2, is a way of carrying 4 PCIe bus lanes out to a pluggable drive - 32GB/s for PCIe version 3.

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