SATA and eSATA

In this video from ITFreeTraining I will look at SATA and eSATA. SATA has become the dominant connection used to connect internal storage devices in computers so it is important to know about it.

Download the PDF handout: http://itfreetraining.com/handouts/ap/1c35.pdf

PATA/SATA
0:11 To understand SATA better, let’s first look what was used before SATA. Parallel AT Attachment or PATA was first developed in 1986. It used a 40-pin ribbon cable that could support two devices on the same cable. The cable transferred 16 bits at a time in parallel. It was powered by the Molex power plug. Traditionally the Molex connectors were white in color. Generally, you will find that power supplies sold on the market today will have a few Molex power connectors.

The cable itself has a maximum length of 18 inches or 457mm. Although not a bad length, in modern computers with large expansion cards and other objects in the way, this can make it difficult to connect devices to the cable. This gets more complex if you want to remove a device from a computer. Due to its short length, you may need to disconnect the cable from the computer or disconnect the cable from another device to remove the device from the computer. This makes it harder to plug in and unplug devices.

The ribbon cable is also quite bulky and thus can block air flow. The PATA cables were the dominant cable until the year 2000 when the SATA cable was released. SATA stands for Serial AT Attachment.

The SATA connection uses a 7-pin data connector and a 15-pin power connector. It increases the length of the cable to 3.3ft or 1 meter. There were a lot of small improvements; the biggest improvement was that SATA supports hot swapping. Hot swapping is being able to plug in an unplug storage devices without having to switch the computer on or off.

Hot swapping requires a few things. First, the computer or the device not being damaged when it is installed. This can occur with electronics when something is first plugged in, as there may be a rush of power to the device. The second thing hot swapping requires is for the device and the operating system to be able to recognize a device was installed or removed. Although hot swapping is officially supported, it sometimes won’t work. For hot swapping to work, it requires the motherboard, BIOS and operating system to support it. You won’t damage anything by plugging it in and giving it a go, and if it fails to work, give the computer a restart and it should detect the device.

Let’s have a closer look at how SATA works.

Data Connector
2:35 The SATA data connector is an L-shaped connector. This prevents it from being plugged in the wrong way. The data connector has seven pins. The data is transmitted using differential signaling. Differential signaling uses two wires to transfer data. This helps reduce noise and data corruption at high speeds – something that is essential when you are using serial communication. The other pins in the cable are ground pins.

Since two pins are used for transmitting data and two for receiving data, this essentially means that SATA has one data channel. When differential signaling is used and there is bi-directional transfer like this, it is often referred to as a lane of data. So essentially SATA supports one lane.

There are other data cables on the market that use more than one lane. This is one of the reasons, which I will cover in more detail later in the video, why it is unlikely in the long term that SATA will continue to be used.

SATA Power Connector
3:36 The SATA drives use a new power connector. Like the data connector, this connector is an L-shaped connector, so you won’t be able to plug it in the wrong way. This power connector has 15 pins. It contains 12 and 5 volt pins that were traditionally provided by the Molex power connector. However, it also adds a 3.3 volt pins.

Since it contains an extra voltage, if an adapter is used to convert Molex to SATA power, it will not include the 3.3 voltage. However, this is generally not a problem because very few storage devices use the 3.3 voltage option.

We know that SATA supports hot swapping, so next I will look at how this is supported, particularly now that we have up to three different voltages on the one power connector.

Description to long for YouTube. Please see the following link for the rest of the description. http://itfreetraining.com/ap/1c35

References
“The Official CompTIA A+ Core Study Guide (Exam 220-1001)” Chapter 3 Lesson 10783-11012
“CompTIA A+ Certification exam guide. Tenth edition” Pages 298-303
“Serial ATA” https://en.wikipedia.org/wiki/Serial_ATA
“eSATAp” https://en.wikipedia.org/wiki/ESATAp

Credits
Trainer: Austin Mason http://ITFreeTraining.com
Voice Talent: HP Lewis http://hplewis.com
Quality Assurance: Brett Batson http://www.pbb-proofreading.uk

Видео SATA and eSATA канала itfreetraining