Kingston "512MB" SD flash cards - only 488MB

Peter wrote:
I have three of these, all brand new. All show 488MB as the size when
formatting them and this is matched by the size of the files that can
be transferred to them from a PC.

Even allowing for 1k being 1024 etc this is a very big shortfall.

Is this normal? I haven't seen it on 128MB and 256MB SD cards.

They are used in PDAs to store GPS moving map data.

488*1024*1024=511705088 ... not far off

It's the same with hard disks. Most manufacturers define a MByte as
having 1,000,000 bytes and most OS's define it (correctly) as
1024*1024=1048576 bytes. Plus you've got formatting overhead for
whatever file system you are using.

FWIW my el cheapo Lidl sourced 512MByte SD card gives a capacity of
513,015,808 bytes or 498MBytes formatted as FAT.
--
Alun Saunders

Alun Saunders wrote:

FWIW my el cheapo Lidl sourced 512MByte SD card gives a capacity of
513,015,808 bytes or 498MBytes formatted as FAT.

Sorry for the typo, that should read 489MBytes

--
Alun Saunders

Peter writes:
Is this normal? I haven't seen it on 128MB and 256MB SD cards.

Yes, it's normal, I think the cards have lots of spare sectors to
allow remapping for write wear. I've seen it in smaller cards too.

As the matter of fact this is an international standard (1MB==1000B).
IMHO this is very reasonable considering the size of the consumers market share.
And the megabytes that the computer and other technically savvy people got used to (2^10), are in fact called MiB.
I don't recall the exact name of that standard but I did see it at some point.,,


Alun Saunders wrote:
Peter wrote:

I have three of these, all brand new. All show 488MB as the size when
formatting them and this is matched by the size of the files that can
be transferred to them from a PC.

Even allowing for 1k being 1024 etc this is a very big shortfall.

Is this normal? I haven't seen it on 128MB and 256MB SD cards.

They are used in PDAs to store GPS moving map data.


488*1024*1024=511705088 ... not far off

It's the same with hard disks. Most manufacturers define a MByte as
having 1,000,000 bytes and most OS's define it (correctly) as
1024*1024=1048576 bytes. Plus you've got formatting overhead for
whatever file system you are using.

FWIW my el cheapo Lidl sourced 512MByte SD card gives a capacity of
513,015,808 bytes or 498MBytes formatted as FAT.

--
Yuri Pismerov, Sr. System Administrator,
TUCOWS.COM INC. (416) 535-0123 ext. 1352

There is 512MB on the card. In order for it to be reasonably useful to a
computer it must be organized in some way. So the formatting process creates a
file system and this is what is consuming all of that space. My 64MB MMC card
has 60.9MB free after formatting. That is about 5% overhead in both cases.

If you don't need a file system then the full 512 MB is available.




Peter wrote:
I have three of these, all brand new. All show 488MB as the size when
formatting them and this is matched by the size of the files that can
be transferred to them from a PC.

Even allowing for 1k being 1024 etc this is a very big shortfall.

Is this normal? I haven't seen it on 128MB and 256MB SD cards.

They are used in PDAs to store GPS moving map data.


Peter.
--
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Please do NOT copy usenet posts to email - it is NOT necessary.


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David W. Schultz
http://home.earthlink.net/~david.schultz

Just because you wind up naked doesn't make you an emperor. - M.A. Padlipsky

In message , Peter
wrote

I have three of these, all brand new. All show 488MB as the size when
formatting them and this is matched by the size of the files that can
be transferred to them from a PC.

Even allowing for 1k being 1024 etc this is a very big shortfall.

1k is actually 1000 when referring to hard disks, and presumably SD
cards.

A computer may report 1k byte as 1024 bytes. M$ Windows reports both
figures.

Converting from the true figure to the alternative (approximate) form of
reporting size gives

(512 x 1000 x 1000) / (1024x1024) = 488

--
Alan

In message , Alun Saunders
wrote

most OS's define it (correctly) as 1024*1024=1048576 bytes.

Er, no. The 1000x1000 figure is correct

The majority of data sheets for memory chips that I've seen give the
exact number of elements rather than the 'shorthand' and often
misleading Mbyte figure.

A manufacturer is more likely to quote a figure of 1048576 memory
locations rather than saying 1Mbytes or 1.04Mbytes. Often memory chips
don't come in sizes that conform to exact byte boundaries - they often
have locations usually used by designers for parity checking etc.

The marketing department will use the figure that appears to be larger


--
Alan

Alan wrote:
In message , Alun Saunders
wrote

most OS's define it (correctly) as 1024*1024=1048576 bytes.

Er, no. The 1000x1000 figure is correct

It depends on your definition of "correct", I suppose.

Ever since I've been working in the computer field, which is getting for
27 years now, a kByte has been 1024 bytes and a MByte has been 1048576
bytes, at least for RAM, ROM and suchlike. I can't honestly say whether
hard disks way back then (which were in the order of 5 or 10 MBytes)
used that or the 10^6 version, and let's face it with capacities like
that the absolute difference between the two is pretty small, but I
still find it misleading to use one definition for memory and another
for storage purposes, and historically I find the 1 MByte=1048576 bytes
the more "correct" one. You can think what you like, however.

--
Alun Saunders

Found it:

http://physics.nist.gov/cuu/Units/binary.html

Yura Pismerov wrote:


As the matter of fact this is an international standard (1MB==1000B).
IMHO this is very reasonable considering the size of the consumers
market share.
And the megabytes that the computer and other technically savvy people
got used to (2^10), are in fact called MiB.
I don't recall the exact name of that standard but I did see it at some
point.,,


Alun Saunders wrote:

Peter wrote:

I have three of these, all brand new. All show 488MB as the size when
formatting them and this is matched by the size of the files that can
be transferred to them from a PC.

Even allowing for 1k being 1024 etc this is a very big shortfall.

Is this normal? I haven't seen it on 128MB and 256MB SD cards.

They are used in PDAs to store GPS moving map data.



488*1024*1024=511705088 ... not far off

It's the same with hard disks. Most manufacturers define a MByte as
having 1,000,000 bytes and most OS's define it (correctly) as
1024*1024=1048576 bytes. Plus you've got formatting overhead for
whatever file system you are using.

FWIW my el cheapo Lidl sourced 512MByte SD card gives a capacity of
513,015,808 bytes or 498MBytes formatted as FAT.

On Sat, 05 Feb 2005 19:45:37 +0000, Alun Saunders
wrote:

Alan wrote:
In message , Alun Saunders
wrote

most OS's define it (correctly) as 1024*1024=1048576 bytes.

Er, no. The 1000x1000 figure is correct

It depends on your definition of "correct", I suppose.

How about the SI units?

Ever since I've been working in the computer field, which is getting for
27 years now, a kByte has been 1024 bytes and a MByte has been 1048576
bytes, at least for RAM, ROM and suchlike.

True, and they've incorrectly been using SI prefixes all the time!

You do know that a Kg is not 1024g, and a Km is not 1024m, right?

I can't honestly say whether
hard disks way back then (which were in the order of 5 or 10 MBytes)
used that or the 10^6 version, and let's face it with capacities like
that the absolute difference between the two is pretty small, but I
still find it misleading to use one definition for memory and another
for storage purposes, and historically I find the 1 MByte=1048576 bytes
the more "correct" one. You can think what you like, however.

How many bits per second can you send down a 1 megabit/sec line?

It has *never* been anything than 1,000,000. Because frequencies
(1MHz) have always been correct.

Still, in the early days, disk manufacturers sometimes quoted
capacities in units of 2000 sectors, each of 512 bytes, i.e. 1024000
byes (also called "megabytes").

The correct prefix for the binary power is "Mebi", written "Mi", as in
"Mebibytes" (MiB).

Malc.