There are two possible methods that Solid State drives use to give us the incredible speeds that they do. An SSD can be designed by the manufacturer to work in Synchronous, in Asynchronous mode or in Toggle mode (which is a mixture of both).

Picture of a Toggle NAND-type SSD

Corsair Force GS Toggle NAND-type SSD.

Which is better? Asynchronous SSDs, Synchronous SSDs or Toggle SSDs? This is a subject that is not quite as clear cut as one might expect. Superficially, synchronous memory operation is theoretically much faster than asynchronous operation. However, the factor that seems to affect the difference between synchronous and asynchronous SSDs the most,  is how compressible a file is before it is written or read. Those files which are un-compressible (like .ZIP files, .JPG files or .MP3 files) will tend to be written and read slower than un-compressed stuff (like .DOC files, .DWG files or .PSD files) because the controller chip itself does a lot of compressing.  Asynchronous v. Synchronous merely refers to the method of access to the storage memory chips (the NAND chips) themselves.

Real World Differences between an Asynchronous and a Synchronous SSD

  • Windows startup: Synchronous is up to 40% faster
  • Movie Replay: Similar
  • Photoshop Image loading : Synchronous is up to 20% faster
  • Gaming : Synchronous is up to 60% faster
  • File copying – compressed:  Similar
  • File copying –  uncompressed: Synchronous  is up to 70% faster
  • Small file writing: Asynchronous is a touch faster
  • Image rendering: – Similar

Technical Stuff

An SSD consists of a controller chip and what is called NAND flash memory. There are two NAND types: ONFI 2.x synchronous and ONFI 1.0 asynchronous.
You can happily skip this part if you aren’t a techie.
If you are technically interested, ONFi 2.x uses timing circuitry which triggers data movement on the rise and also on the fall of the square wave clock signal. This works on a similar principle to Double Data Rate RAM and is capable of delivering speeds up to 133MB/s. ONFi 1.0  works like single data rate RAM where  data movement is triggered on the rising clock pulse only. This limits speeds to just 50MB/s. So it sounds as if synchronous mode is more than double the speed of asynchronous,  but because of the actual electronic architecture, the effective difference is much less.
Toggle NAND memory chips boosts peak read performance and faster write performance for small files by utilizing a complex hybrid system of Synchronous and Asynchronous triggering modes.

The bottom line:

Asynchronous SSD = inferior performance but are cheaper
Synchronous SSD = superior performance and more expensive
Toggle SSD = superior performance and best value for money

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