It’s been about 9 months since I blogged on Samsung’s public roadmap and the fact that it carried some 3D Stacked DDR4 Devices using Through Silicon Vias (TSVs). Time for a quick update…
A customer asked us, “Do I need DDR4 write CRC beyond a certain frequency?”
The answer is far from simple; it’s dependent on many factors including the type of system it is, the other types of error correction (ECC) that may be in use, the system’s tolerance of errors, and the system’s ability to spare the bandwidth required for the write CRC function. Since I’ve been asked a few times and since the answer is so complex, I created the flowchart here to show some paths through the possible choices.
I have written on the topic of Row Hammering in a White Paper I published last year (link here) but since it is in the spotlight recently I thought I’d dedicate a blog entry to it. I had never considered this to be a security hole until this morning.
Samsung has posted their DDR4 product guide on their website, and it gives us excellent insight into the direction that Samsung plans to go with DDR4 in the next few months with a lot of data that wasn’t previously publicly available.
A lot has been written about DDR SDRAMs, both the compute variety (DDR3/4) and the mobile variety (LPDDR3/4) and what may come after these technologies run their course. One thing is certain; the future will not be an easy path for DRAMs. The DDR protocol based on a wide parallel bus with single ended signaling and a source synchronous data strobe and non-embedded clock is not scalable beyond the data rates currently specified for these technologies. After DDR4, the world will need something else as the DDR interface cannot realistically be expected to run at data rates higher than 3200Mbps in a traditional computer main memory environment. Unfortunately, that something else will likely be “somethings” else. Likewise, the smartphone’s insatiable need for higher bandwidth from main memory DRAM will also lead to a deviation from the wide parallel bus based DRAM.