SATA is two different things: a physical connector standard and a logical communication bus.
When SATA was first designed, the two were linked.
In fact, the physical SATA connector can only use the logical SATA bus.
However, the SATA bus can be accessed over newer physical connectors.
In this article, well cover both.
Contents
The SATA Bus
In computing, a logical bus is a communication protocol to transfer data.
SATA stands for Serial AT Attachment.
The AT isnt technically an acronym to avoid patent infringements.
It is based on IBMs predecessing Advanced Technology Attachment (ATA) standard, which was later renamed PATA.
The P standing for Parallel to differentiate it from the Serial bus.
The SATA protocol was first standardized in 2003.
The first generation of the SATA protocol supported 1.5Gbs of bandwidth.
This allowed for up to 150MBs of usable bandwidth with overheads considered.
High-speed HDDs can actually exceed these transfer speeds.
SATA II doubled the supported bandwidth, then SATA III doubled the bandwidth to 6Gbs.
This exceeds the capabilities of any HDD but can be a limiting factor for SSDs connected via SATA.
The power connector is wider than the data connector, making it easy to distinguish.
The power cable plugs into the drive directly from the PSU.
In contrast, the data cable will connect the drive to the motherboard.
Other Connectors
There are a small variety of secondary connectors included in the SATA standard.
However, most were short-lived and cant be found in modern devices.
Outside of the SATA standard, the physical M.2 connector supports transferring data over the SATA bus.
Any M.2 SSD should actively advertise if it connects via NVMe or SATA.
If it doesnt, theres a fall-back method.
The M.2 connector standard defines different cut-outs for other use cases, referred to as keys.
NVMe M.2 drives will only have an M key.
The M key has a cut-out after five pins from the right.
The B key has the cut-out after 6 pins from the left.
Most M.2 SATA drives have both keys cut out, making them easy to identify.
Typically, it is connected to the NVMe bus for high-speed connectivity.
But with the B key, data instead runs over the SATA bus.
This has the same limitations as the standard SATA connectivity and does not support any extra bandwidth.
Any M.2 slot will only have a single key cut-out, depending on which bus it connects.
This makes it impossible to accidentally connect an NVMe M.2 SSD to a SATA M.2 port.
Additionally, this would be non-standard and may not be supported by the BIOS.
What is SATA Good for in a Modern Computer?
SATA is primarily useful for storing data where the writing and reading of said data are not time-sensitive.
For example, suppose you want to save a word document.
SATA isnt ideal when speed is an essential factor, or substantial transfers are likely to happen.
For example, suppose you want to edit 4K 60fps video footage.
In that case, the bandwidth SATA offers simply isnt enough to do this in real-time.
Similarly, these will take longer over a slow SATA connection if you want to perform large system backups.
Critically it will also take longer to restore from a backup over SATA.
Early SSDs used the connector because it was already standard, making market adoption easier.
Additionally, early SSDs were much slower than modern drives due to low levels of technological maturity.
