SD card: 1G vs 2G

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Man-wai Chang

What are their difference?

Why is a card reader able to read the 1G but not the newer 2G card?

Thank you in advance!
 
What are their difference?

Why is a card reader able to read the 1G but not the newer 2G card?

Thank you in advance!
Click to expand...

Some are a different density and the reader has problems with it - the
same as early computers when larger capacity DIMMS came out - they'd see
a double sided one but only half the capacity of a single sided high
density.
 
Man-wai Chang said:
What are their difference?

Why is a card reader able to read the 1G but not the newer 2G card?

Thank you in advance!
Click to expand...

http://en.wikipedia.org/wiki/SDHC#SDHC

"Standard-SD cards (non-SDHC) with greater than 1 GB capacity

According to the specification,[19] the maximum capacity of a
standard SD card is defined by (BLOCKNR × BLOCK_LEN), where
BLOCKNR may be (4,096 × 512) and BLOCK_LEN may be up to 2,048.
This allows a capacity of 4 GB. The main problem is that some
of the card readers support only a block (or, sector) size of 512 bytes,
so greater than 1 GB non-SDHC cards may cause compatibility difficulties
for users of such devices."

"SDHC

To increase addressable storage, SDHC uses sector addressing instead
of byte addressing in the previous SD standard."

So up to 1GB, byte addressing, with 512 byte blocks, should always work.

Devices bigger than 1GB, may need larger sector size, like 2048 bytes.

And once over 4GB, the standard changes to SDHC.

Paul
 
This allows a capacity of 4 GB. The main problem is that some
of the card readers support only a block (or, sector) size of 512 bytes,
so greater than 1 GB non-SDHC cards may cause compatibility difficulties
for users of such devices."
So up to 1GB, byte addressing, with 512 byte blocks, should always work.
Devices bigger than 1GB, may need larger sector size, like 2048 bytes.
Click to expand...

You meant if I formatted a 4G SD card using 512-byte blocks, the old
card reader might be able to read it like it did with older 1G SD cards?
 
Some are a different density and the reader has problems with it - the
same as early computers when larger capacity DIMMS came out - they'd see
a double sided one but only half the capacity of a single sided high
density.
Click to expand...

Further detail? :)
 
Man-wai Chang said:
You meant if I formatted a 4G SD card using 512-byte blocks, the old
card reader might be able to read it like it did with older 1G SD cards?
Click to expand...

I don't think you can "format" the thing to fix it.

http://en.wikipedia.org/wiki/Talk:Secure_Digital

"Some SD-card reader systems does not correctly process the READ_BL_LEN
parameter. And therefore will not correctly recognise some cards
(esp 2G and 4G cards in std sd-card readers). But this is NOT the
same as saying >1GB - 4GB standard sd-cards doesn't exist or will not work."

The fields are c_size, c_size_mult, read_bl_len. Once the c_size and c_size_mult
are approaching their maximum value, the only way to declare a larger SD, is to
use a larger read_bl_len.

It appears Sandisk has on occasion released info in document form, and this
is just one example of showing some of those register values. In this particular
example, the device has a small enough capacity, that a 512 byte read_bl_len
can be used.

http://www.cs.ucr.edu/~amitra/sdcard/ProdManualSDCardv1.9.pdf

Paul
 
If it's a built in card reader, a driver update may allow the
use of 2GB cards. I have a 5 year old HP laptop that
initially wouldn't recognize 2GB SD cards. A driver update
fixed that.
Click to expand...

It's an Oregon Scientific CU328 indoor phone.
 
1GB SD are only $6.25 each. Buy a handful and you're all set.
Each one has more capacity than a CDROM.
Click to expand...

Thank you again! I was just curious about the generation gap...
 
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