Six years ago I was the engineering design manager for a small defense
oriented firm which has been making instrumentation for US Navy ships
since well before WWII. One problem with making instruments for US Navy
ships is the Navy's desire to have them continue to function despite
large explosives detonating in their immediate vicinity.
We had previously produced a line of navigational displays using a flat
panel color display and a single board computer but running with a
2-1/2" notebook hard drive for storage. Notebook hard drives are pretty
rugged but we were always concerned about survivability during "the
depth charge test". You mount your equipment on a small barge and 60
pounds of dynamite is set off in the water a short distance away. The
equipment must be running before, during and after the explosion. We
always got the equipment to survive but... not necessarily on the first
go around
Once CF cards had achieved 64MB we decided to do a design using CF cards
as a replacement for the hard drive figuring they were essentially
totally shockproof. I remember at the time being very concerned about
wear out failures since, despite the wear leveling controllers in CF
cards the stated life from the manufacturers at that time was (as best I
can recall) about 100,000 write cycles. Anyhow, 64MB was the magic
number that appeared to allow us to run entirely in RAM with no swapping
back to the drive and thus no unpredictable write counts.
I'm sorry to say that those early CF cards did cause us problems and we
had somewhat more field failures than with notebook hard drives.
However, we never found out *why* they failed. Some set of evidence
pointed to curious IT type sailors who couldn't keep their hands out of
the box to see what was inside with no hard drive.
A long story to get to the main point which is if CF cards can be
written to with abandon with regard to life cycle then the technology
has changed a great deal from six years ago.
Chuck Norcutt
Moose wrote:
> John Hudson wrote:
>> I use 2GB compact flash cards with my E500. I shoot in RAW mode.
>>
>> I use a Verbatim MicroDrive and Windows Explorer to download the images to
>> my PC and then use the Olympus software to process the images. I delete all
>> images from the card excepting only the last one.
>>
>> Does the compact flash card have a finite life in terms of the number of
>> images that can be written by the camera? If there is a finite life how many
>> images can be written by the camera before the card dies?
>>
> Yes, they can wear out
> No, it won't happen in practical use.
>
> The individual bits in flash memory have a limited life. In fact, the on
> card controller distributes writes across the whole card, so the bottom
> part won't wear out first.
>
> However, the number of cycles is so high that the chances of any heavily
> working pro wearing one out before it becomes technologically obsolete
> is nil.
>
> From the Wikipedia entry. http://en.wikipedia.org/wiki/Flash_memory
>
> "With these mechanisms in place, some industry analysts have calculated
> that flash memory can be written to at full speed continuously for 51
> years before exceeding its write endurance, even if such writes
> frequently cause the /entire/ disk to be overwritten. This figure (51
> years) involved a worst-case scenario using specific data parameters and
> should not be confused with a particular "shelf life" for a flash memory
> device. The bottom line is that a typical user using a commercial
> device, such as a camera, with a flash drive will probably not wear out
> the memory for the effective life of the camera."
>
> Moose
>
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