Received this unsolicited e-mail today:
From: "aheadsz23567" aheadsz23567@aliyun.com
Sent: Tuesday, August 27, 2013 11:32:10 PM
Subject: RE:Best Quotation of micro SD memory card
Hello Sir ,
Hope you have a good day ,
Have you find a good supplier for the SD / Micro sd cards ?
HongKong Famous International Trade Co., Ltd here offering you a best price as below :
Kingston Micro SD/TF card price:
Capacity price
1GB 1.64$
2GB 1.88$
4GB 2.65$
8GB 3.85$
16BG 6.87$
32GB 11.56$
MOQ : 600pcs (minimum order quantity)
Warranty : 5 years
Package : Retail / Bulk / Plastic
Just stay in touch with us for further questions , Glad to serve you,
Simon Chuck
Sales Manager
Best Regards & Thanks
I'll be looking for some cards once I get the next Bobuino revision going and I get the 16-bit ADC/DAC stuff added, but I don't think I'll need 600!
I could grab 10pcs or so but 600 pcs is pretty crazy.
I wonder how many of those cards will be DOA and if the seller will become mysteriously unreachable for warranty claims.
I also wonder if they're really Kingston or just have the letters K, i, n, g, s, t, o, and n written on them.
I've noticed that cheap flash devices of the same make and model all come up with a slightly different total capacity as reported by Windows Disk Manager. I assume the bad cells are subtracted from the nominal capacity. So a "16GB" card might be closer to 14GB after all the bad blocks are hidden.
There are lots of counterfeit Samsung, Kingston and SanDisk SD cards on ebay.
I've noticed that cheap flash devices of the same make and model all come up with a slightly different total capacity as reported by Windows Disk Manager. I assume the bad cells are subtracted from the nominal capacity. So a "16GB" card might be closer to 14GB after all the bad blocks are hidden.
Genuine SD cards have a large number of spare blocks and always report the same capacity since bad blocks are remapped.
My recent SanDisk 8 GB class 4 cards all report 15523840 blocks and 4 GB class 4 cards report 7744512 blocks. I used my development version of the SdFat SdInfo example to determine the block count.
The spare blocks are used as a pool of erased flash blocks and are mapped to the correct logical block number when written.
Manufacturers do change the size of cards. Many manufacturers changed from MLC flash with two bits per cell to TLC flash with three bits per cell. This makes a major change in the flash controller and the block count.