Re: undersized compact flash cards?

[Tom Ritchford <tom@swirly.com>]

>May be of interest to Repeater owners:
>
>http://www.theregister.co.uk/content/3/21454.html

tony.smith@theregister.co.uk wrote:
>What we think it's trying to say is that a SanDisk megabyte is 48,576 
>bytes
>smaller than everyone else's. So, if you buy a 64MB SanDisk CompactFlash
>card, you'll actually get 3,108,864 fewer bytes than you expect.

There are only two possibilities:

1. SanDisk's disks come in exactly the same sizes as everyone else's
    but SanDisk reports *everyone's* sizes differently.

or

2. SanDisk's disks ARE somehow smaller and they use this weird
    accounting to conceal this fact.


Now, they only MAKE chip memory in certain very round sizes:
1,2,4,8,16,32,64,128,256 megabits for example(*),
where a megabit is 1024*1024 bits or 2**20 bits.

All the CompactFlash manufacturers are using similar
commodity chips.

So all the cards pretty well have to come in exactly
the same sizes.  You'd really have to go out of your
way to disable 5% of the memory!

The only reason might be if they were using part of
the memory somehow for something clever like error
correction.  But you think they'd trumpet this fact!

No, I think it's option 1...


        /t

(* -- Not all that memory is always available to you because
the CompactFlash card also has to keep directory information,
but that also has nothing to do with the manufacturer,
it's part of the standard (or else different disks couldn't
be read by different machines!))


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