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Old 23 March 2015, 13:52   #17
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Join Date: Jun 2010
Location: PL
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Originally Posted by Mrs Beanbag View Post
Nothing is safe.

What is Row Hammer?
In the quest to get memories smaller and faster memory vendors have had to make trade offs. One of these is very small physical geometries. These small geometries put memory cells very close together and as such one memory cell’s charge can leak into an adjacent one causing a bit flip. It has come to the attention of the industry that this is indeed happening under certain conditions. Very simply the problem occurs when the memory controller under command of the software causes an ACTIVATE command to a single row address repetitively. If the physically adjacent rows have not been ACTIVATED or Refreshed recently the charge from the over ACTIVATED row leaks into the dormant adjacent rows and causes a bit to flip. This failure mechanism has been coined ‘Row Hammer’ as a row of memory cells are being ‘hammered’ with ACTIVATE commands. Once this failure occurs a Refresh command from the Memory Controller solidifies the error into the memory cell. Current understanding is that the charge leakage does not damage the physical the memory cell which makes repeated memory tests to try to find the failing device useless.
Btw this problem is known from at least 2003...
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