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[OM] Re: First CF card failure

Subject: [OM] Re: First CF card failure
From: Chuck Norcutt <chucknorcutt@xxxxxxxxxxxxxxxx>
Date: Sun, 28 Oct 2007 17:55:32 -0400
When I said this was my first CF card failure I wasn't telling the 
complete story.  This was my first CF card failure where the CF card was 
being used in a camera.

Some number of years ago when a 64MB CF card was considered new and 
huge I happened to be the engineering design manager for a small company 
developing products for the US Navy.  One of the products we made was a 
navigational display for aircraft carriers which incorporated a small 
computer and hard drive and a color LCD panel.  One of our major 
problems with products for the Navy was getting them past the shock 
test.  In short, the product was bolted to the deck of a barge floating 
in a rock quarry where a 60 pound charge of dynamite was set off next to 
the barge.  The requirement was that the product had to be running and 
fully functional before and after the explosion.  Hard drives and glass 
display panels tend to take not too kindly to this test.  Since 64MB CF 
cards had just come on the market we considered them large enough to 
take the place of the hard drives.  Being solid state we figured it 
would be much more likely to survive the shock test.  In the process I 
had to investigate the likely life of the cards.  I don't know what it 
is today but back then a CF card sector was typically quoted as having a 
life of 100,000 write cycles which is facilitated by wear leveling. 
Wear leveling is a process whereby heavily used sectors are logically 
swapped for infrequently used ones so that the wear is distributed 
evenly across  the card.  We figured 100,000 write cycles was way more 
than enough since the disk was mainly a program loading device with very 
little write activity.  We eventually did encounter a few premature 
failures at sea but our product inspections indicated it was most likely 
due to curious techie sailors who couldn't keep their hands out of the 
gear.

Anyhow, the manufacturers claims at the time were for 100,000 write 
cycles for each sector.  That says you'd have to fill your CF card 
100,000 times before it fails.  The 128MB card I first wrote about was 
unlikely to have had been filled even 50 times.

Chuck Norcutt

Bob Whitmire wrote:
> Thanx. Figured as much. Just read somewhere else that CF cards (or  
> any in-camera image storage, for that matter) have a limited  
> lifespan, perhaps more limited that we might tend to think. Wish I  
> could recall where I read it.
> 
> --Bob
> 
> 
> On Oct 28, 2007, at 12:02 PM, Chuck Norcutt wrote:
> 
>> Just to let you know that, tough as they are, they do eventually fail.
> 
> 
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