Memory Myth


I’ve been using different memory cards in different devices. I’ve used MMCs, SD, MicroSD, Sony Memory stick and so on. I never bothered re-checking their capacity and trusted on the label on the card itself. I have been using a 2GB MMC-Mobile in my good old N72 and I never went into the phone’s memory monitoring software to see actually how much memory is available on the card. Recenly I got a SanDisk’s 16GB SDHC card and when I plugged it into my Nokia N82, it reports it as 15GB. Thats loss of a whole GB of data capacity. Then I plugged it into my BlackBerry and found that it reports it to be 14.8GB. Another 200MB lost. Then I decided to actually try a few other cards around. I investigated a little further. I plugged my 8GB Micro-SDHC card in my BlackBerry and it reported it to be 7.6 GB. Thats again not 8GB. Then I plugged a common 1GB Micro-SDHC card into my Nokia N82 and it reports it to be 964 MB.

The key point is, I never noticed the capacity loss on 1GB card because its only 60MB. While on a 16GB card its losing a whole 1.2GB.

Why is that happening? I revisitied my basic data capacity and storage unit concepts. Let me list down a few basic facts for you.

1 kilo-byte = 1kB = 1024 bytes
1 megabyte = 1MB = 1024kB = 1024×1024 bytes
1 gigabyte = 1GB = 1024MB = 1024x1024x1024 bytes

Therefore
16GB = 16 x 1024 x 1024 x 1024 bytes.

In reality, what memory card manufacturers do, they put it as follows:

1 GB card has slightly more than 1000,000,000 bytes.
It s hould actually be 1073,741,824

Similarly, 16 GB card actually has 16,000,000,000 bytes. This makes the total to 14.90GB

So if you buy 1GB, you should expect actully something less than that.

The thing which is bothering me is, my Nokia reports my 16 GB card as 15GB, while my BlackBerry reports it as 14.8, while it actually is 14.9 GB.

I’m pretty close in above calculation, but where do you think I’m going wrong?

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