8 Gigabyte Sandisk MicroSDHC Incompatibility

[David Garabana Barro]

On Friday 21 May 2010 12:26:42 Al Johnson wrote:

> > Hi,
> >
> > I have a Kingston SDC4/4GB-2ADP : 4GB SHDC which shows write errors when
> > access are not aligned on a boundary. I've first suspect a problem with
> > the Freerunner has the problem only arise when booting from this SD
> > card.
> > But I've tested it latter with a USB card reader (Transcend M5) and
> > found problems when random reading/writing on a partition.
> > I've retried with 1MB aligned partitions and found that everything was
> > going well.
> >
> > So aligning partition is not only a matter of performance, for some card
> > it's also a requirement.
> >
> > To align partition with fdisk from util-linux use the following options:
> >
> > c  - toggle msdos compatibility flag
> > u  - set unit to sectors instead of cylinder
> >
> > See for example:
> > http://old.nabble.com/-ANNOUNCE--util-linux-ng-v2.17.1-td27685302.html
>
> Very interesting. I've not seen that mentioned for SD cards before. I have
> one of those that's resisted all other attempts to get it working reliably
> in a Freerunner, but the same partition table is fine when the card is in a
> usb card reader, or the SD slot on my netbook. I'll have to give this a
> try.

Yes, it's really interesting.

I've had troubles with the same Brand on FR, but the 8 GB version  (Kingston 
SDC4/8GB)
Now I'm using it on a usb key, but without partitions at all.
I think there is the key:
People use sd cards without partitions. Even Windows XP doesn't recognice 
partitions but the first one. That's why manufacturers doesn't bother to say 
that partition alignation is required.

Now I'm using a 16GB trascend on FR, without problems. 

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