6GB/sec or 6Gbit/s?

Need someone to help me understand the difference between bit & byte, i understand the 8Bits = 1Byte.  But question is what is faster data transfer rate 6GB/sec or 6Gbit/s?  Comparing the 2 following SDD's


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In this particular case, the speed is 6 Gigabits per second, for BOTH SSDs (and in fact, for ALL modern SSDs).

6Gb/s is describing the maximum theoretical speed of the SATA III interface, which the SSD is compatible with. It is not describing the speed of the SSD itself.

It is measured in bits, because this is a measurement of bandwidth.

Your computer uses the SATA interface to communicate with the hard disk. There are a number of different revisions to the SATA interface depending on the age of your computer, which determines the maximum speed they can operate at:

   SATA I  =   1.5 Gigabits per second,  or roughly 187 Megabytes/s
   SATA II =   3.0 Gigabits per second, or roughly 375 Megabytes/s
   SATA III = 6.0 Gigabits per second, or roughly 750 Megabytes/s

The SSDs on the TigerDirect website are simply indicating that they are compatible with the SATA III interface. They often explicitly state "6Gb/s" to help avoid confusion with SATA II's maximum speed of "3" Gbit/s, and the name SATA "3".

Both of these SSDs, and in fact pretty much ALL modern SSDs, are compatible with the SATA III interface, which can run at the same maximum speed of 6 GigaBITS per second.

However, this is only the maximum theoretical speed of the SATA bus itself, NOT the speed of the disks. In reality, the disks will be much slower. Also the measurement of speed TigerDirect suggests in the title, e.g. "Up To 540 MB/s Read Speed, Up To 520 MB/s Write Speed" is also a gross over-exaggeration, only achievable under ideal circumstances which you will rarely encounter during the normal use of the disk... much like the advertised mileage of a car. In real life, the disks will be significantly slower.

The exact speed depends on a lot of factors which is very hard to quantify.

The best way to compare two SSDs is to look up their benchmark scores - synthetic number that were obtained by running real tests on the disks themselves, letting you compare them apples-to-apples.


The Samsung EVO benchmarks 5519, one of the fastest on the market.


The other disk doesn't even have a listing on Passmark, which makes me suspicious.

The EVO seems like the clear winner here.

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ManieyaK_CSSPAuthor Commented:
Thanks for the quick response & good description.
If you're interested in diving into the nitty gritty of the Samsung 840 EVO, check out AnandTech.com's in-depth review of it here:


This review also demonstrates why we need benchmark scores for the average user- and how a simple benchmark score doesn't tell the whole story - there's an awful lot of variables to factor in when evaluating performance!
ManieyaK_CSSPAuthor Commented:
FrostySSS thanks for that  i will most definitely check it out.
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