As CPU makers push microprocessors even faster, a PC’s memory must keep up as well. JEDEC, a key chip standards body, has responded by issuing a new DDR5 memory standard that pushes speeds up to 8800Mbps.
Put another way, that means that PC memory speeds will increase from DDR5-6800 to DDR5-8800, eventually. Memory makers as well as PC processor vendors will have to support the new standard, and modules will have to be manufactured and tested. But the official announcement means that the clock has started.
The new specification is officially known as JESD79-5C.
There’s another wrinkle: the inclusion of Per-Row Activation Counting (PRAC), a feature of the new specification. “PRAC precisely counts DRAM activations on a wordline granularity,” the release says. “When PRAC-enabled DRAM detects an excessive number of activations, it alerts the system to pause traffic and to designate time for mitigative measures.”
This appears to be a security measure, designed to counteract a type of memory hack known as “Rowhammer.” As the name suggests, Rowhammer attacks repeatedly access, or “hammer,” a row of transistors on a memory chip. Over time, the persistent attacks could cause a transistor on a nearby row to flip. Theoretically, at least, that could lead to the otherwise protected memory leaking data. Anandtech suspects that PRAC is there to help mitigate Rowhammer attacks, and that’s probably right.
It appears that PRAC allows the “hammered” memory to cool down, in effect, which could help stop Rowhammer attacks in the future. It’s not an attack PC users typically have to worry about, but it’s one that could help keep your cloud data safe.