Memory shortage on micro SD cards!

derrick

Can someone please explain why memory capacity on SD cards is always short of stated?

Following is via My Computer, then properties of cards;-

Kingston 16GB micro SD card fully formatted;
Used space 132MB
Free space 14.4 GB
Capacity 14.6GB
Shortfall = 1.4/6 GB of memory!

Kingston 8GB micro SD card fully formatted;
Used space 96.0 KB
Free space 7.41 GB
Capacity 7.41GB
Shortfall = 0.59GB of memory!

What is the "used space" on a fully formatted card?
And why so much on the 16GB as against the 8GB?


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scheming_gypsy

it's the way they format, you don't get the full capacity - even on hard drives.

derrick

scheming_gypsy wrote: »

it's the way they format, you don't get the full capacity - even on hard drives.

So they are allowed to decrease the stated capacity by 10%?

I wonder how people would feel if they bought a 2 litre car and found the engine cc was only 1.8 litre?
Surely this would come under the trades description act?

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paddyrg

If you look up 'FAT32', you can find a detailed answer to this question - what it boils down to, though, is that some space gets lost due to partially used blocks/sectors, the file allocation table (and its duplicate) and some other odds and ends.

k9387

Advertisers use a multiple of 1000 where as computers use a multiple of 1024 when going from kilobytes to megabytes, megabytes to gigabytes, etc.

You also loose more space with the formatting overhead.

John_Gray

scheming_gypsy wrote: »

it's the way they format, you don't get the full capacity - even on hard drives.

NO - it's mostly because disk manufacturers measure capacity in billions of bytes: 160 GB is 160 billion bytes to them- whereas everyone else measures then as multiples of 1024 bytes, so 160 GB is 160 x 1024 x 1024 x 1024 =171[SIZE=-2] [/SIZE]798[SIZE=-2] [/SIZE]691[SIZE=-2] [/SIZE]840 bytes.

So your nominal 16 GB SD becomes 14.9 GB - and there is some additional minor reduction because of the file system overheads.

Maybe read about the difference between gigabytes and gibibytes! The latter, although useful, is rarely encountered, and the confusion persists.

k9387

derrick wrote: »

I wonder how people would feel if they bought a 2 litre car and found the engine cc was only 1.8 litre?
Surely this would come under the trades description act?
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You will quite often find they are not, a 2 litre may well be 1999cc or less.

My Honda 1000rr, even though it has 1000 in its name is only 998cc.

derrick

k9387 wrote: »

You will quite often find they are not, a 2 litre may well be 1999cc or less.

My Honda 1000rr, even though it has 1000 in its name is only 998cc.

Yes but a couple of cc's doesn't matter, the difference on the SD cards is 10%, and that on your Honda would equate to it only being 900cc, I think you would be miffed about that, and on a 2 litre would mean 1800cc!

I can understand to a point some space being used for "overheads", but the 16GB card states Used space 132MB
Free space 14.4 GB
Capacity 14.6GB
Shortfall = 1.4/6 GB of memory!
So if only 132MB of used space, where is the extra 1GB+ of space that is missing?

Thanks all for the info, it looks like the consumer is stuffed again! I still think this is misleading and possibly illegal advertising.
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spannerzone

It's not lost in 'overheads' as such.... it's about how there are different methods used to report the same data. Hard drive makers and other manufacturers measure their storage devices using the 'SI' international system of units whereas computers (or the operating system) usually measures in binary

For further light reading: http://johnofe.com/nonfurry/byte/index.htm

I suppose it's a little bit like the gallon, there's the imperial gallon (4.54litre) and the US gallon (3.78litre).

poppy10_2

derrick wrote: »

So if only 132MB of used space, where is the extra 1GB+ of space that is missing?

Thanks all for the info, it looks like the consumer is stuffed again! I still think this is misleading and possibly illegal advertising.
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Read John Gray's answer above. Nothing illegal here.

Mr_Toad

derrick wrote: »

Thanks all for the info, it looks like the consumer is stuffed again! I still think this is misleading and possibly illegal advertising.
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Not really. As others have said it's as much to do with people's understanding of the technology and it's terms as anything else.

I know when I buy a memory stick or drive the formatted size will be less than the unformatted size on the box.

As John said Computers use Gb = 1024 * 1024 * 1024 while manufacturers use Gb = 1000 * 1000 * 1000 because it's easier for the human brain to work with. You can turn 15998753177 into Gb by shifting the decimal point 9 places to the left. Dividing by 1024 three times isn't something most people can do in their head.

Have you told Windows to show you hidden and system files and folders, you may find there are things like $recycle.bin and System Volume information using space.

As well as looking for hidden files and folders have you checked to see if there is a hidden partition on the device. I've had USB sticks that come with 'free' applications which are sometimes in hidden partitions.