How much/what hardware does the rowhammer DRAM bug affects?

grarpamp grarpamp at
Wed Sep 16 20:46:26 PDT 2015

On Wed, Sep 16, 2015 at 4:03 PM, jim bell <jdb10987 at> wrote:
>>From: Georgi Guninski <guninski at>
>>This is old, but haven't seen it here.
>>Rowhammer” is a problem with some recent DRAM devices in which
>>repeatedly accessing a row of memory can cause bit flips in adjacent
>>It was able to use this to gain write access to its own page table, and
>>hence gain read-write access to all of physical memory.
>>There is POC.
>>Variant via javascript:
>>How much/what hardware does this bug affect?
> This brings me back to my stint at Intel, 1980-82, as a new Product Engineer
> for the 2186, an 8kx8 pseudostatic (self-refreshing dynamic) RAM. (One of
> the first DRAMs to use redundancy to increase yield.)  I may have been the
> first engineer in the world to see, through a microscope focused on a DRAM
> chip, a very quick series of flashes, evidence of the programming (blowing)
> silicon fuses on the chip, to program the row- and column-redundancy
> information.
>  Product engineers were, and presumably still are, responsible for writing
> test programs to run chips through their paces, in Intel's case using a
> Teradyne computer.
> I don't think the concept of this kind of weakness is new:  Even in 1980,
> DRAMs were tested for such repeated accesses, to ensure that such errors
> would not occur.  This was particularly true for a process called "device
> characterization", in which chips were attacked in all manner of
> electronically-abusive ways, to uncover these weaknesses, and fix the
> circuit design should such flaws be uncovered.
> One way these techniques could be thwarted is to return to the use of
> parity-bits (8+1 parity) in memory access, in DRAM module and computer
> design, to whatever extent they are no longer used.  Any (successful)
> attempt to modify bits in a DRAM would quickly end up causing a parity
> error, which would at least show which manufacturer's DRAM chips are
> susceptible to this kind of attack.  A person who was forced to use a
> no-parity computer could, at least,  limit his purchases of such modules to
> those populated with DRAMs not susceptible to the problem.
>            Jim Bell

Some paper has said systems using ECC RAM are resistant / immune
to rowhammer.

There is still a fair bump in cost for ECC system
however once you've seen your first syslog entry
you forget about the cost. Regardless of rowhammer.

More information about the cypherpunks mailing list