antispam@math.uni.wroc.pl wrote:
> It seems that most (maybe all) cards are programmable.  There was
> a blog post some years ago explaining how to reprogram a card.
> Makers of fake cards used small card and reprogramed it to
> report larger size.  You need to get hold of program for
> faking cards and use it to change card info.  Sorry,
> I do not remember links, you would have to do searching
> yourself.

I did wonder about using fake cards.  There's this:
https://hackaday.com/2013/12/29/hacking-sd-card-flash-memory-controllers/
which is not really a practical attack unless you know which specific cards
are being targeted.

The fake card manufacturers likely have a tool to reprogram whatever
microcontroller is in their cards, but I've not seen such things available.

I suppose I could buy one of those '1024GB' cards and hope that they put in
a really slow controller as well as at least 4GB of actual flash...

Theo

Theo <theom+news@chiark.greenend.org.uk> wrote:
> 
> I have a setup with a micro SD card which may be suffering signal integrity
> issues.  One suggested remedy is to try it with a slower card.  I had some
> success with a 2GB Class 2 card from the dark ages, but 2GB is too small to
> test properly.  There's nothing I can really change about the setup - it
> appears the speed selection is happening in ROM, so if I put in a fast card
> the faster speeds get enabled, and then fail.
> 
> So I'm looking for 8-32GB micro SD cards that don't support all the fancy
> modern speed grades.  Most of the market is advertising how speedy they are. 
> A scour of Amazon has found some class 4 cards.  I have class 6 and class
> 10 cards that don't work.
> 
> I had a look around industrial SD cards and they also make a big thing of
> speed.
> 
> So are there any SD cards that can somehow be programmed to only run the
> slowest speed modes, in a way that will persist over power cycle?

It seems that most (maybe all) cards are programmable.  There was
a blog post some years ago explaining how to reprogram a card.
Makers of fake cards used small card and reprogramed it to
report larger size.  You need to get hold of program for
faking cards and use it to change card info.  Sorry,
I do not remember links, you would have to do searching
yourself.
 

-- 
                              Waldek Hebisch

I have a setup with a micro SD card which may be suffering signal integrity
issues.  One suggested remedy is to try it with a slower card.  I had some
success with a 2GB Class 2 card from the dark ages, but 2GB is too small to
test properly.  There's nothing I can really change about the setup - it
appears the speed selection is happening in ROM, so if I put in a fast card
the faster speeds get enabled, and then fail.

So I'm looking for 8-32GB micro SD cards that don't support all the fancy
modern speed grades.  Most of the market is advertising how speedy they are. 
A scour of Amazon has found some class 4 cards.  I have class 6 and class
10 cards that don't work.

I had a look around industrial SD cards and they also make a big thing of
speed.

So are there any SD cards that can somehow be programmed to only run the
slowest speed modes, in a way that will persist over power cycle?  Or a
source of larger cards that only implement the older SD v2.0 spec?

I suppose one option would be a non-SDHC 4GB card, which just might be big
enough with some trimming and probably use SD 2.0.  But I don't know those
were ever produced in the micro size.

Any suggestions?

Thanks
Theo