The serial number of the normal card, for example, is 0x9C62CAE6, or decimal 2,623,720,166 - a much more feasible serial number for a popular product like a microSD card. The chance of me “just happening” to get the very first microSD cards out of a factory is pretty remote. Other cards in the irregular batch also had similarly very low serial numbers, in the hundreds to thousands range. Also, the serial number is very low - 0x960 is decimal 2,400. Dates are counted as the offset from 00/2000 in the CID field, so a value of 00/2000 means they didn’t bother to assign a date (for what it’s worth, in the year 2000, 2GB microSD cards also didn’t exist). When we read out the electronic card ID data on the two cards (available through /sys entries in linux), this is what we found:įirst, the date code on the irregular card is uninitialized. It turns out the weirdness in the external markings is just the start of it. The broken D is something found on SanDisk cards, but Kingston cards found in US retail almost universally use a solid D. Typically, brand name vendors like Kingston would be very picky about the accuracy of their logos. The second strange issue, perhaps more subtle and perhaps not damning, is the irregularity in the “D” of the microSD logo. This is in contrast to the card on the right, which is laser-marked, and has a lot code that varied with every tray of 96 units. In fact, across the entire batch of irregular cards, they shared the exact same lot code (N0214-001.A00LF) (typically the lot code will vary every couple hundred cards at least). Silkscreening a lot code on isn’t that unusual, but typically the silk does not share the same stencil as the logo, so you’ll see some small variance in the coloration, font, or alignment of the lot code from the rest of the text. The most blatantly strange issue is that the card on the left has its lot code silkscreened using the same stencil as the main logo. I’ve put red arrows on the details that called the most attention to me at first. On the right is a sample of a normal card. On the left is a sample of the irregular card. The first thing that raised my suspicions is the external markings on the irregular Kingston cards. Also, memory cards aren’t cheap the spot price on this type of memory card is around $4-5, so it’s a few thousand dollars in scrap if we can’t get them exchanged … and neither chumby nor the CM is large enough to sneeze at a few kilobucks. Second, there was a lot of them - about a thousand all together, and chumby was already deeply back-ordered. First, Kingston wouldn’t take the cards back because we had programmed them. Normally, the story would end there you’d RMA the material, get an exchange for the lot, and move on. Sure enough, after subtracting these cards from the line, yield was back to normal again. I had the factory pull the entire lot of microSD cards from the line and rework all the units that had these cards loaded. After poking and prodding a bit, I realized that all the units failing had Kingston microSD cards from a particular lot code. A call came in from the floor noting that SMT yield had dropped dramatically on one lot, so I drove over to the building to have a look (this is the advantage of being in China during production - you can fix problems like this within the hour, before they become really serious issues). It all started back in December of 2009, when chumby was in the midst of production for the chumby One. It is actually snapshot of a much longer forensic investigation to find the ground truth behind some irregular Kingston memory cards. The microSD ware for January 2010 was not an incidental post.
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