Ben NanoNote microSD performance?

David Kuehling dvdkhlng at
Sat Sep 11 06:58:53 EDT 2010

>>>>> "Alan" == Alan Post <alanpost at> writes:

> On Fri, Sep 10, 2010 at 02:54:21PM +0200, David Kuehling wrote:
>> Somewhat related issue that I wanted to report some time ago:
>> when running Debian from micro-SD, micro-SD writes put a *very*
>> strong load on the system, with a kernel process "irq/22-MMC/SD"
>> burning 100% cpu cycles.  This was so bad, that even keypresses won't
>> be correctly recognized (presumably the IRQ that reads the keyboard
>> matrix ran too seldomly).  Pressing a key once, one ended up with
>> like 100 keystrokes, because the kernel thought a key had been held
>> for many seconds, although that was just the too slow keyboard
>> sampling.
>> I wonder whether these problems somehow depend on the micro-SD card
>> used?  How much variation is possible in how a micro-SD card
>> implements the SDIO protocol (like variations in transfered block
>> size).
>> Now I bought a class-6 card, hopefully that's better (didn't try
>> yet).

> David,

> I don't have any information about this problem, but I will be
> interested in hearing how the class-6 card goes, if you do test it in
> the next few days.

Just did a 1:1 image copy from old to the new class-6 micro-SD card and
booted that (Debian Sarge on top of the Openwrt-xburst kernel).
Sometimes it still misses (short) keypresses when writing to the SD card
(like doing an apt-get update).  When it runs out of RAM and swaps to
the card, it gets worse, then it still sometimes duplicates pressed keys
a few times. 

Still better than the card before.  I wonder if anybody can boot Debian
From microSD without these kind of problems?

CPU load of the MMC IRQ now mostly stays below 70%.

This is a 4GB Transcend Class 6.  It says TS4GUSDHC6 on the back of the
packaging, which cost <EUR 12.


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