I just got a new mmc card today and I decided to benchmark it (along with my old card) via hdparm.

In my card reader which is connected to my desktop computer hdparm -t gives me:

• 18 MB/sec on my old class 4 card
• 12 MB/sec on my new class 2 card

However in my n810 I only get

• 5.2 MB/sec on my old class 4 card
• 3.5 MB/sec on my new class 2 card

I used hdparm from easyDebian.

Setting CPU to performance mode gives me slightly better numbers, but never more than 4.3 MB/sec for the class 2 card. This alone is confusing, because I was expecting the card itself to be the limiting factor and the CPU's influence should be neglectable.

What is going on here? The numbers from my desktop seem to be a bit too good but the ones from my n810 seem too bad. I would expect something around 8 MB in both cases. What am I missing?

May be your card reader has a buffer?