SD Card Question

[Guest RussellH]

Just bought a Sandisk 128MB SD card from my local Orange store for use in an SPV M2000. When I checked the memory to see if it was working, it shows total storage card memory of only 120.03MB, In use = 0.00MB, Free = 120.03MB. Is there some reason why this would be right, am I doing something wrong, or is there a problem with the SD card? I can't understand why nearly 8MB has just disappeared!

Thanks.

[Guest Chaser81]

Could be to do with the formatting of the card, have you tried re-formatting it in the M2000?

[Guest RussellH]

Thanks for the reply Chaser81.

No, I haven't formatted it. How do I do that? I can't see any option in settings.

Thanks,

Russell

[Guest maxh2003]

I can explain this one :-)

It's (essentially) a scam by SanDisk and other disk manufacturers (e.g. Maxtor).

Windows (arguably correctly) considers a kilobyte to be 1024 bytes, a megabyte to be 1024*1024 = 1048576 bytes, and a gigabyte to be 1024*1024*1024 = 1073748124 bytes.

So, for Windows to show a card as exactly half a gigabyte, the card should have 1073748124 / 2 = 536,870,912 bytes.

But, SanDisk - and virtually every other disk manufacturer - defines a kilobyte as 1000 bytes, a megabyte as 1000*1000 = 1,000,000 bytes and a gigabyte as 1000*1000*1000 = 1,000,000,000 bytes. That means their half-gigabyte card has 500,000,000 bytes - 36,870,912 bytes less than Windows thinks a half-gigabyte card should have.

In the case of a 128Mb card:

Windows: 1048576 * 128 = 134,217,728 bytes

SanDisk: 1000000 * 128 = 128,000,000 bytes

The difference between those two figures accounts for 6,217,728 bytes = 6,072K = 5.92 megabytes, of the discrepancy between SanDisk and Windows.

The rest of the discrepancy is for the file allocation table (FAT) which allows filenames to be linked to the correct parts of the disk space.

For comparison purposes, my brand-new "300Gb" Maxtor drive showed about 276Gb once formatted. A scam, whether the drive manufacturers agree or not, because (most) people don't actually get what they thought they were paying for.

More information here -> http://www.answers.com/topic/mebibyte-1

[Guest RussellH]

Thanks for the explanation maxh2003.

At least it means there isn't a fault with the card.

[Guest pd.ryder]

A very good explanation O:)

It doesn't stop me from grumbling about having only 499Mb on my 512Mb SD card :roll:

[Guest dj_sea]

only 499mb! thats pretty bad...