One of those nasty little secrets about DRAM is that bits may get corrupted by simply reading the bits in a different part of the chip. This has been given the name “Row Hammer” (or Rowhammer) because repeated accesses to a single one of the DRAM’s internal “rows” of bits can bleed charge off of the adjacent rows, causing bits to flip. These repeated accesses are referred to as “hammering”.
Although this was once thought to be an issue only with DDR3 DRAMs, recent papers (listed on the DDR Detective) show that DDR4 also suffers from Row Hammer issues, even though DRAM makers took pains to prevent it.
One big champion of this phenomenon is Barbara Aichinger (pictured) of FuturePlus Systems, a test equipment maker that specializes in detecting row hammer issues. The Memory Guy has had the pleasure of talking with her about this issue and learning first-hand the kind of difficulties it creates.
How does Row Hammer work? It stems from the fact Continue reading “What is DRAM “Row Hammer”?”