Comparing the physical size of 1960'ish core store -
How the devil do they test these microSD? Is production so good these days that they just test a sample?
So they take a £5 deposit to put you on a waiting list then if you don't like the price you don't get your fiver back...but it is amazing what you can get on a card nowadays .
I know that's for mobile phones but as for memory cards in general I'd be cautious about using a high capacity card ( depending on what you are using it for ) ...I'd be more inclined to use several cards so that if one went pear shaped you at least have the others ..although facilities like photoRescue are pretty good at recovering lost images should the worst happen . .
No, they generally test the lot.
writing a falsh catr all one sor all 0s is fast. So is reading it off. So hey can generally get a clear idea if there are dead cells at that level. Wring the whiole card with two or theree random patterns carefully chosenm may detect whether the cells are leaking 'next door' so to speak. This takes buyt seconds.
I also suspect there may be a way in which 'bad sectors' are written out of the system as well. Just like with disks. They have an area where block with surface imperfections are taken out of use.
BUT given crystal purity and clean machines, its unusual to find a chip that doesn't either work perfectly, or fail immediately and obviously.
And that's what customer returns are for. Let the customer do the final test.
But testing keyboards to check that keys generate the correct letters/numbers etc clearly has some way to go .:-)
That's certainly true of Enterprise NAND flash, and because you find bad cells when you write to them (unlike a disk where you tend to find them mostly on reads, unless they're so bad you can't even find the sector header at write time), the NAND flash controller can remap at that point without losing data. Although there's no dedicated area, and because of wear leveling, erase-ahead, and block replacement, the actual mapping of block numbers to flash cells changes all the time.
Actually, it's normal to have some blocks which don't work on new devices. That's hidden from you by the flash controller.
Must admit that whilst I know (and lecture on) Enterprise grade NAND flash, I don't know anything like as much about the consumer grade NAND flash used in USB sticks, IPODs and the like, but my personal observation is that consumer flash is nowhere near as reliable (or as expensive;-).
I use a Panasonic HD recorder at work. Records over 90 minutes of HD pictures and 8 tracks of audio on two cards that would both fit in a matchbox. At the end of the day's 'filming' the material gets transferred to HD and the same cards re-used the next day. Not heard of any failures in over a year's worth of use across three units. Just as well given what they cost...
There's always a first time .lol... I took a studio set of images on a couple of CF cards but when I went to load them to my PC one had few if any images showing up. Luckily I have Photo Rescue and recovered all but a couple but it had me sweating for a bit . .
Usenet Nutter wibbled on Thursday 10 December 2009 16:30
I got caught out by a SanDisk CF card going bad on me on the holiday of a lifetime. Now I always burn in new cards with "badblocks" under linux (similar tools exists for windows) a good 3-4 times before I start using it.
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