Cat 4 and Cat 10 micro SD cards have about same performance in two tests on the Ben!

Delbert Franz ddf at
Wed Oct 10 19:35:23 EDT 2012

I have just run some simple tests to see if there is much difference 
between using a Cat 4 and a Cat 10 micro SD card in the Ben.  I have 
two Bens now and two Cat 4 32 GB cards and two Cat 10 32 GB cards.  
The Cat 4 cards are made by Transcend: one is made in Taiwan and the 
other in China.  One of the Cat 10 cards is made by Samsung and the 
other by Sandisk.  

The first test was to transfer an ASCII file with a size of about 14 
MB from my desktop to each Nanonote, doing it for two different cards.  
The scp command was issued on the desktop computer and the Nanonotes 
were connected via USB to that computer as well, to reduce network 
overhead.  Public/private keys were used so that no password was 
entered.  The average transfer speed for the Cat 4 cards was: 580 KB/s 
(K=1024) and for the Cat 10 cards was: 620 KB/s.  That's an increase 
of transfer speed of about 7 per cent.  

This change is much less than the alleged change in the maximum 
transfer rate for each of the two categories of cards.  Not much 
advantage to using a Cat 10 card:-) This probably follows from the many 
layers of software involved in such a transfer over USB.  Lots of 
factors contribute to transfer speed.  For example, a larger file 
would have had a faster rate in that the hand-shaking at the start of 
the transfer adds a second or two of time.  

The second test was compiling and linking a C program with 73 small 
C-program files at opt level 2.  This makes heavy use of swap space so 
perhaps the Cat 10 cards would show some advantage.  The time for the 
Cat 4 cards, averaged over both cards and both Nanonotes was 713 
seconds.  The time for the Cat 10 cards was 666 seconds.  This is a 
decrease in time of about 7 per cent.  However, it turned out that one 
of the Cat 10 cards had an average time 4 seconds longer than one of 
the Cat 4 cards!  So again, real-world performance may not have much 
relationship to the category assignment.  Many other factors enter 
into real-world performance.  
Comparing the fastest Cat 10 card with the slowest Cat 4 card on the 
compiling test showed a decrease in time of about 13 per cent.  Not 
much given the difference in cost for these two categories.  

My overall conclusion is that for these two test, the difference 
between Cat and Cat 10 is quite small.  Often ratings of hardware are 
based on conditions that maximize its performance.  Real-world 
applications often do not show much difference. 
It would be interesting to have a small sample of cards of the same 
category and same maker and then test them.  I suspect that there 
would be variations between cards nearly as large as I found here.  
However, I do not want to spend more time on that.  Getting precision 
in benchmarking is difficult given the complexity of modern OS's and 

So save your money and buy a Cat 4 card for the Nanonote:-) 


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