Found this article when researching what brand of microSD card to buy, the author found some irregularities in some Kingston memory, then went to a Chinese flea marketplace to buy up all kinds of samples and tested them electronically and also chemically dissolved the plastic coating to see what was inside:
http://www.bunniestudios.com/blog/?p=918 Short Excerpt from the article: Here are the most interesting high level results from my survey: The normal Kingston cards (samples #2 and #3) were all direct Toshiba OEM cards (MID = 0x000002, OEMID = 0x544D (ASCII TM, presumably for Toshiba Memory)). These cards employ Toshiba controllers and Toshiba memory chips, and seem to be of good quality, and thankfully the only ones that were sent on to chumby customers. The irregular card (sample #1) uses the same controller chip as the outright fake (sample #4) that was bought in the SZ market. Both the irregular Kingston and the fake Kingston had low serial numbers and whacky ID information. Some of these cards experience some difficulty in normal operation. I still hesitate to call Kingstons irregular card a fake thats a very strong accusation to make but its construction is similar to another card of clearly questionable quality, which leads me to question Kingstons judgment in picking authorized manufacturing partners. The irregular card is the only card in the group that does not use a stacked CSP construction. Instead, it uses side-by-side bonding. The only two memory chip foundries in this sample set were Toshiba/Sandisk and Samsung. Note that Sandisk and Toshiba co-own the fab that makes their memory chips. Samsungs NAND die the most expensive part of a microSD card is about 17% larger than Toshiba/Sandisk. This means that Samsung microSD cards should naturally carry a slightly higher price than Toshiba/Sandisk cards. However, Samsung does get to offset that against the ability to diversify the same die from microSD packages into street-packaged TSOP devices, and they also dont have a middleman like Kingston to eat away at margins. Overall, the MicroSD card market is a fascinating one, a discussion perhaps worth a blog post on its own. Id like to point out to casual readers that the spot price of MicroSD cards is nearly identical to the spot price of the very same NAND FLASH chips used on the inside. In other words, the extra controller IC inside the microSD card is sold to you for free. The economics that drive this are fascinating, but in a nutshell, my suspicion is that incorporating the controller into the package and having it test, manage and mark bad blocks more than offsets the cost of testing each memory chip individually. A full bad block scan can take a long time on a large FLASH IC, and chip testers cost millions of dollars. Therefore, the amortized cost per chip for test alone can be comparable to the cost of silicon itself. _______________________________________________ Hardwarehacking mailing list [email protected] http://lists.blu.org/mailman/listinfo/hardwarehacking
