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Synchronous or Asynchronous SSD Models: Does it Make a Difference?

It is hard not to miss the fact that many manufacturers of SSDs offer two models that are only different in price by a small margin and state fairly close performance specifications. While on the surface this seems like an advantage because you can get almost the same performance for less, the real truth is not so rosy.

Although controllers on all SandForce-based drives are essentially the same, firmware versions can be different which can make a difference in performance. The other major factor is type of flash memory. The fastest type of flash memory is synchronous flash memory such as made by Toggle. This is considered to be some of the highest quality memory available. One way for a manufacturer to offer a lower-priced offering is to use cheaper asynchronous flash memory instead.

Without getting into all the technical details, synchronous flash memory is a newer technology that allows data processing seemingly twice as fast as asynchronous flash memory. The reality is not nearly that clear cut but it is a very different story compared to what the specifications say.

The design of SandForce SSD controllers employs on-the-fly data compression to achieve some of the remarkable performance. What this means in practice is that highly compressible data such as text files and source code can achieve much faster performance than very incompressible data such as JPEG photos, h.264 or MP4 video files, and application binaries.

Because of this difference it is not unusual for SSDs to be evaluated based on compressible data performance and incompressible data performance. Numerous articles bear out the exact differences in performance but the bottom line is that a SandForce SSD using asynchronous flash memory will be substantially slower in many real world tasks than a model that employs synchronous flash memory.

Some common examples of synchronous versus asynchronous models include the following models with the asynchronous offering listed first: the OCZ Agility 3 versus the OCZ Vertex 3, the OWC Mercury Electra 6G versus the OWC Mercury Extreme Pro 6G, and the Corsair Force 3 versus the Corsair Force GT.

Also note that the Crucial M4 SSD models also include synchronous flash memory and are a very good alternative to SandForce-based designs. They are also a very good value.

Looking at the Corsair Force 3 versus Corsair Force GT (which I previously covered in two articles) the difference in price is not very substantial. When asynchronous and synchronous SSD models first became available together, the price difference was closer to $100 or more between two comparable. Let’s see where the difference in price is now.


The smallest drive in the Force 3 or Force GT series is a 60GB SSD. The Force 3 version costs $99.99 while the Corsair Force GT 60GB costs $110.49. A difference of $10.50 is more than worth the substantial performance benefit to the Force GT. The cost per gigabyte in the two versions is $1.67 versus $1.84.

Looking at the more commonly-used 120GB size, the Force 3 comes in at $169.99 versus the Force GT 120GB at $189.99. Once again, the $20 difference in price is a small price to pay for a substantial performance benefit that the Force GT affords. The cost per gigabyte for the Force 3 is $1.42 as compared to the Force GT’s $1.58.

Stepping up to the 240GB size offers a similar picture. The Force 3 is sold for $314.99 while the Force GT 240GB affords a premium at $374.99. The difference here amounts to $60 which is a little more of an actual cost difference. While the 60GB models commanded a 9.5 percent price increase to move to the Force GT and the 120GB commanded a 10.5 percent increase, the 240GB models command a 16 percent price premium for the Force GT model. For the 240GB models, the cost per gigabyte is $1.31 and $1.56 respectively.

The highest capacity model in each lineup is the 480GB model and the price difference becomes a little more dramatic. The Force 3 comes in at $682.49 while the Force GT 480GB comes in at $826.99. This time the difference is $144.50 between the models. The cost per gigabyte is $1.42 for the Force 3 and $1.72 for the Force GT. The price increase works out to be a 17.5 percent premium.

The Bottom Line

If you are already spending the money on an SSD because you know the major performance gains that will be achieved, I would recommend against scrimping at the last minute to save a few dollars. SSDs are not an inexpensive upgrade but do represent a dramatic performance increase and are one of the best upgrades that can be done to any system. For a $10, $20, or $60 increase in price, you could realize nearly double the performance for some operations, particularly those that commonly happen in real life. Once you hit the 480GB models, you most likely will buy the fastest model if you are already willing to put that much money into an SSD.

Corsair Force GT 180GB

The most important model in the lineup to me is one that I did not include in the results above. Surprisingly, the 180GB Force 3 is $249.99 while the 180GB Force GT is $254.99 right now. For only a $5 difference in price and an amazing value of only $1.42 per gigabyte, the Corsair Force GT 180GB remains my pick for the best performance, size, and value in an SSD.