NAND FLASH It is now a very important storage medium , According to the factory test results, it can be divided into the original film （ Positive ）、 White and black .

The so-called original film is NAND FLASH The best wafer selected by the manufacturer , Cut it down and package it into finished products after various tests , At this time, the finished product will be tested , What passes the test is the original film , Those who fail the test are white films , When cutting the original film, the rest is black , There may be various problems .

In terms of performance, it is the original film > White tablets > Black film . There are almost no problems with the original film , White film may have some problems , There is a problem with the black film probability （ Such as capacity , Reading and writing speed, etc ）. Then the original film is produced and sold by the manufacturer , White films are sold to downstream manufacturers , Black chips are treated as garbage .

When black chips are used as garbage, they will be deducted （ fall code） Handle , So the black film becomes ID Incorrect , Wafer with abnormal data reading and writing . But the manufacturer has a set of command data that can make “ Die ” Of NAND FLASH“ resurrection ” Of , This is the so-called release （DECODE） 了 .

Because black chips are treated as garbage , So the purchase price is very low , But it can be normal after unlocking NAND FLASH Use , There is a huge price difference between them .
The release code is generally different from manufacturer to manufacturer , However, some manufacturers share the same set because of the previous agreement , Such as Toshiba and SanDisk NAND FLASH Share one set , Toshiba's NAND FLASH ID Become Shandi's NAND FLASH ID, therefore NAND FLASH change ID It can only be changed between two specific manufacturers .

One thing needs to be clarified , Unbuttoned NAND FLASH The capacity of is FLASH Actual capacity of , So there is no 8GB Of NAND FLASH After the deduction, it becomes 8GB Real capacity +8GB False capacity （ Total capacity 16GB） The situation of . Usually original NAND FLASH What's the maximum capacity of , Deblocking changes ID Then the capacity will not increase ,

But there are some exceptions , such as B0KB It can be released into L06B, This is a direct change FLASH Properties of , from MLC Change into TLC. Generally, the deduction is unchanged FLASH Property of , Turned out to be TLC, After the deduction, it's still TLC, such as 7THL Even from Toshiba to SanDisk , In a broad sense, both Toshiba and SanDisk are called 7THL.

There are usually two ways to release , The first is the second solution ： After the deduction NAND FLASH Can be used normally , And power off and then on NAND FLASH It is still in the state of release . The second is three solutions ： After the deduction NAND FLASH Can be used normally , But power off and then on NAND FLASH It will be in the state of missing deduction .

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