[UKids] Glueing SD cards into XO laptops

Arnd Bergmann arnd at arndb.de
Sat Mar 26 18:04:12 EDT 2016

On Monday 21 March 2016 11:13:41 Adam Holt wrote:
> Not our first choice, but the reason we are forced to consider this hack
> (despite our distaste for sleeves/converters that sometimes fail) is that
> full-size SD's are increasingly harder to procure --  as these are no
> longer mass-market items: the increased price of full-size SD's can
> (sometimes) destroy viability.

This sounds surprising to me. Looking at a price comparison site, I can
see the following:

* There are about 10% more models of microSDHC cards available compared
  to SDHC, currently 663 vs. 593

* For the larger SDXC cards, the reverse is true, with 199 SDXC vs
  147 microSDXC.

* For faster cards, there are also more SDHC than microSDHC. This is
  particularly important because slower cards are likely to use TLC
  flash rather than MLC, and they will die fast

* Looking at the most common models from reputable manufacturers
  that are available in both sizes:
  - Sandisk Ultra 2015:       SDSQUNC-032G-GN6MA / SDSDUNC-032G-GN6IN
  - Sandisk Extreme Pro 2015: SDSQXNE-032G-GN6MA / SDSDXNE-032G-GNCIN
  - Samsung EVO 2015: MB-MC32DA / MB-SC32D
  - Samsung PRO 2015: MB-MD32DA / MB-SD32D
  in each case, the SDHC model is cheaper than the respective microSDHC
  model, in case of the last one much cheaper (19 vs 26 EUR).

You probably don't want to get any other model than the above ones
anyway, but if you do then make sure that they are comparable in
their performance and longevity characteristics and you are not
comparing cheap microSDHC cards that are only meant for storing
videos to the ones that have a chance of surviving a few months
of use as a normal file system for user data.


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