Understanding SD Cards and the Smart Way to Use Them

by planetMitchLeave a Comment

I found this article some time ago (i don't remember where I'm afraid) and thought it was incredibly interesting and wanted to share with everyone. I prefer CF cards because I'm constantly losing SD cards (and they're so darn flimsy)

I don't know if this applies to CF cards as well, but I'm betting some of it applies.

It all kind of scares me to tell the truth… we rely on these dang things so much!

Why the same type of SD card can work just fine, or drop frames like mad.

From Frank Glencairn:

Memory cards are incredible unreliable.

First you have to understand the way, how flash memory cards are made. They are not just flash chips, but they are much more complex engineered than you think.

Most of them are jammed with defects all over the place. That’s why there are dirt cheap (0.9 Nano-Dollars per bit). Memory cards are incredible unreliable The only reason why they work for you (except when they don’t work of course), they come with pretty sophisticated controller chips, that do all the error correction and bad block management under the hood. This is necessary, cause with every newer, faster, and cheaper fabrication process (that happens about every 12-15 months), the flash memory becomes even more unreliable. So the manufacturer has to come up with better and faster controllers, and a new set of EEC rules must be applied. So they really have to jump through burning hoops, to make the cards at least appear to be reliable.

Recycling and dirty little secrets under the hood

The quality of flash chips integrated into memory cards varies widely. It can be anything from pristine, spanking new material, to recycled chips with over 80% bad sectors. There is actually a reason, why cards, that have the same specs on paper, can have a way different price tag (and real world performance). Especially the cheaper cards are often made from second class, or even recycled material. Sometimes you can find a 32GB chip in a 16GB card. The missing 16GB are just bad blocks, that are mapped out by the controller chip. Since those controllers cost next to nothing, managed memory is much cheaper than raw flash chips with tightly defined specs. Just ct15 for the controller does the trick, to present the illusion of perfect, reliable data to the user.

SD Cards can work just fine

Companies, who are known for their reliable media, usually have better material, and stricter and better quality control, but even they mix and match flash chips, yet sell the card with the same part number and name.

House of cards

So by using a controller, they can sell almost any bit of the wavers they made, without throwing anything away. That sounds like a win-win situation for everybody, and it usually is. When your USB thumb drive needs 4 more seconds to push the data over to your computer, you probably never know or even care. But when it comes to high demanding use, that pushes those cards on they edge, like recording raw video, the whole house of cards (pun intended) can fall down pretty quick. The controller usually does a good job, but it only can do so and o much, and that may be sometimes not enough, and you start dropping frames.

Yeah, I get it Frank. So what can I do?

Continue reading Frank's suggestion “Why the same type of SD card can work just fine, or drop frames like mad”

   
 Note: it is our policy to give credit as well as deserved traffic to our news sources – so we don't repost the entire article – sorry, I know you want the juicy bits, but I feel it is only fair that their site get the traffic and besides, you just might make a new friend and find an advertiser that has something you've never seen before 
   

(cover photo credit: snap from Frank Glencairn)

planetMitch

chief astronomer at planet5D LLC
Mitch "planetMitch" Aunger is the creator and mastermind behind planet5D.com

He's incredibly happy running planet5D and sharing so much joy of photography and filmmaking with his readers.

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