4 ms·
How many times more expensive would DRAM that is immune to rowhammer cost?
by nightfly 5y ago
How many times more expensive would DRAM that is immune to rowhammer cost?
- staticassertion 5y agoNot an expert, but I feel like the answer is not much. ECC RAM is not, to my knowledge, considerably more expensive to produce - the reason it costs more is because it only works with specific devices, so it's more of a market cost. ECC RAM is pretty effective as-is against rowhammer, and imo you could very likely tweak ECC's approach to get even further. The 'worst case' solution wouldn't be more than 2x, right? Since you'd just have to keep a clone of RAM, but obviously shuffled so that the same errors wouldn't occur in the same places. So 2x seems like the sort of absurd upper bound, but I feel like we could do a lot better.
- userbinator 5y agoMid 2008 or so I think was when rowhammer-prone DRAM started appearing, so consider the density of that DRAM compared to today.
- Dylan16807 5y agoMy understanding is that rows in memory chips have thousands of bits in them. If you add 10-20 more to act as a refresh counter, then you can trigger extra refreshes if it gets high enough. Done right, that should give you immunity to rowhammer, while only costing a fraction of a percent in extra die space. And you won't be able to trick it like you can hash-table-based refresh counters.