vB Easy Archive - ANSWER TO: Where did my missing MB go in my MMC Card?

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ANSWER TO: Where did my missing MB go in my MMC Card?
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Posted by: friedbrains

i posted this in Nokia Forum, but i thought this is very much needed here as well...

ANSWER TO: Where did my missing MB go?

To understand why your 64MB card has only 60.9MB of space, it is necessary to define what we mean by a MB or megabyte.
The "dictionary" definition of MB, and that which is used by software such as Windows Explorer (or the Palm OS) is that 1 Megabyte is equal to 1,048,576 bytes. This is the case because there are 1,024 bytes in a kilobyte and there are 1,024 kilobytes in a megabyte. Remember that computer capacities are measured in powers of 2. A kilobyte is 2 to the 10th power. A megabyte is 2 to the 20th power.

Manufacturers who produce storage media, however, use a different definition of megabyte: 1 MB = 1 million bytes. It's a simpler definition to understand, but it causes a large discrepancy when you start talking about large numbers of megabytes.

A "64MB card" will hold only 64,000,000 bytes (not 67,108,864 bytes) worth of programs, data, etc. If you divide that by 1024 (the number of bytes in kilobyte), you find that it will hold 62,500 kilobytes. If you divide that number by 1024 (the number of kilobytes in a megabyte), you find that the card will hold only 61MB. The two different definitions "cost" you approximately 4MB on a "64MB card."

It is a confusing concept if you're not used to thinking of bytes, kilobytes and megabytes being determined by powers of 2. What this means, basically, is that if you have a 62MB file (say, a video), it will not fit on a 64MB card.

Note that there is also a chunk of space that is taken by system files, which amounts to around 100k on an MMC card (which is why the 64MB card shows up as 60.9MB; you start with 61MB and subtract about 100k). These system files seem to be much larger (more than 900k) on SD cards, which is why the screenshot of the 16MB card shows only 14MB capacity instead of 15MB.

Also, remember that the discrepancy gets bigger as file sizes get bigger. A 512MB card, which should be available next year, will actually hold only about 488MB worth of data, for a loss of 34MB!

The following table shows the "advertised" and "real" amount of space on various sized MMC cards (SD may be a few hundred kilobytes smaller, from what I can tell so far)..

Advertised------------------Estimated Actual
8 MB--------------------------7.5 MB
16 MB------------------------15 MB
32 MB------------------------30 MB
64 MB------------------------61 MB
128 MB-----------------------122 MB
256 MB-----------------------244 MB
512MB-----------------------488 MB
1 GB--------------------------977 MB

this was taken from http://www.geocities.com/romidar/mmcvssd.htm

Posted by: gforce23

Quote:

Originally posted by friedbrains

Also, remember that the discrepancy gets bigger as file sizes get bigger. A 512MB card, which should be available next year, will actually hold only about 488MB worth of data, for a loss of 34MB!

A 512mb card is already available. HF4, kindly edit the above post..

Posted by: abhi

Common knowledge. There was a discussion on this a few months ago, if im not mistaken. The same point was discussed then.

Posted by: gforce23

Quote:

Originally posted by abhi
Common knowledge.............

Only for engineers like us..

But not for newbies

Posted by: angel_wing0

Quote:

Originally posted by abhi
Common knowledge. There was a discussion on this a few months ago, if im not mistaken. The same point was discussed then.

for u..not for newbies thats for sure!

oops my bad...thought friendbrains wrote it

Posted by: Trekker

should be made a sticky or added to the FAQs

I too did not know this and always thought that i got 122mb coz of the brand of my 128mb MMC (PQI)

Posted by: abhi

ya, well i guess its not that common knowledge after all.

Its a good thing for people to know, so yes, it shd be a sticky, imo.

Posted by: angel_wing0

yip...and other ppl told me that the memory that didnt appeared is being used up in other ways..liek i felt being lied to

Posted by: praz

Quote:

Originally posted by angel_wing0
yip...and other ppl told me that the memory that didnt appeared is being used up in other ways..liek i felt being lied to

lol man and u believed those ppl ?

Posted by: angel_wing0

i know...i dont think the idea of ppl ripping me seems rite to me since every brand never comes with the exact memory amount showed

Posted by: praz

Quote:

Originally posted by angel_wing0
i know...i dont think the idea of ppl ripping me seems rite to me since every brand never comes with the exact memory amount showed

exactly

Posted by: angel_wing0

so yeah..thats why i believe them =P

Posted by: kmx

Wirelessly posted (NokiaN-Gage/1.0 SymbianOS/6.1 Series60/1.2 Profile/MIDP-1.0 Configuration/CLDC-1.0 UP.Link/5.1.1)

I paid $9.50 for a 128mb Mmc card and when i get it comes only 122 of space.

Posted by: Soul814

woh where u get that? i paid $35 for mine... 256 mb :/

Posted by: kmx

Wirelessly posted (NokiaN-Gage/1.0 SymbianOS/6.1 Series60/1.2 Profile/MIDP-1.0 Configuration/CLDC-1.0 UP.Link/5.1.1)

I got it off ebay. I forgot the sellers name. I will post it later on when i get back on my computer. But i foot think he sells mmc's anymore. I think he sells sd cards now.'

Posted by: abhi

Wirelessly posted (Mozilla/4.0 (compatible; MSIE 5.0; Symbian OS; SonyEricsson P800; 316) Opera 6.31 [en])

Quote:

Originally posted by xgagexx
Wirelessly posted (NokiaN-Gage/1.0 SymbianOS/6.1 Series60/1.2 Profile/MIDP-1.0 Configuration/CLDC-1.0 UP.Link/5.1.1)

I paid $9.50 for a 128mb Mmc card and when i get it comes only 122 of space.

Only 10$!! Thats pretty cheap.

Posted by: Trekker

yea.. $10 is very cheap... u should have gotten more and sold them at a profit

I got my 128mb for $25

Posted by: praz

Quote:

damm thats the cheapest price any1 can buy 128mmc for :P
unless and until they get it for free

Posted by: angel_wing0

#10..thats VERY cheap

Posted by: CeluGeek

I always thought that the loss of memory on storage devices was caused by the file system the device (the MMC card in this case) is formatted for.

Posted by: ultra99

hey gforce23
where did u get that game from? what is it called?