The Trend

There is a trend observed in the market for designing products with SuperSpeed USB and NAND Flash inside.  There are camera manufacturers, printer manufacturers as well as FLASH drive manufacturers involved in the trend. It is crucial, at this point of time in the market, to have a proper knowhow on what factors affect such designs and what can be done to achieve a successful and a longlife design.


SuperSpeed USB

The USB 3.0 standard claims that it is 10 times faster than USB 2.0. The theoretical speed is 4.8Gbps (600MBps). However looking at various realistic speed test reports made available by more

than one developers, it has been concluded that 400MBps is the maximum achievable speed for this standard.


Factors affecting performance

Depending on the NAND Flash used in the system, the performance can be estimated. But, there are a number of factors affecting the speed and performance of USB in a system. Eric Huang has listed

the dependencies very interestingly in his blog. I am listing them here.


The USB transfer speed is affected by the following factors:


  • Number of applications running on the host machine
  • The speed of the application itself
  • The quality of the drivers (host as well as device)
  • The bus on the hardware that moves data from USB controller to CPU (on host as well as device
  • side)
  • The USB PHY
  • The USB Cable


Non-ideal system

Looking into a nonidealized system, the SLS SuperSpeed USB Device IP Core tests performed on GigaByte A75 Motherboard have indicated the performance ~2.1Gigabits per second (262.5

Megabytes per second) with mass storage interface and ~2.7Gigabits per second (337.5 Megabytes per second) with raw interface.


There is a word in the development community about NAND Flash being the bottleneck for USB performance.


Lets see how the performance numbers with the NAND Flash look like. Mass storage performance tests with SLS SuperSpeed IP and ONFI controller IP (without ECC overload) have indicated speed

upto 101.5 MBps (812 Mbps).



What does this mean?


  • Transferring 1 Gb (125MB) data from the flash drive to the PC would take a second, which takes more than 6 seconds at present with USB 2.0 interface and RAM memory
  • Copying 5Gb (625MB) data from flash drive to PC would take 5 seconds, which is right now taking 31 seconds using USB 2.0 interface and RAM memory
  • Data that takes 5 minutes to transfer using USB 2.0 interface and RAM at present (6000MB) would be transferred in 48 seconds!


Not bad to have this solution for the current product upgrade...


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