The PC industry hasn't seen an updated memory spec in a while, and it was long past due. That upgrade came last week, as the memory standards group JEDEC revealed that it had published a spec for DDR4 SDRAM, defining "features, functionalities, AC and DC characteristics, packages and ball/signal assignments," that builds on the DDR3 spec, first published in 2007. The DDR4 spec applies to SDRAM devices from 2 GB through 16 GB for x4, x8 and x16 buses. Here's a look at some of the particulars.
“The new standard will enable next generation systems to achieve greater performance, significantly increased packaging density and improved reliability, with lower power consumption,” Macri said.
Double Data Rate
First and foremost, DDR4 memory doubles the maximum transfer rate of DDR3. The new spec supports a per-pin data rate of up to 3.2 giga transfers per second (GT/s), twice that of its predecessor's eventual maximum of 1.6 GT/s (the ceiling was raised over time). And, DDR4's max could likewise go higher, as necessary, to accommodate faster components and bus speeds. So far, the only processor roadmap we've seen in support of DDR4 has been Intel's, with its Haswell server processor slated for 2014; consumer-platform support isn't expected until sometime in 2015.
Meanwhile, JEDEC member company Samsung announced in July that it had begun sampling the "industry's first" 16-GB DDR4 RDIMMs, and that it will also offer a 32-GB module; and Samsung, Micron and other companies already offer smaller-denomination DIMMs that comply with the spec.
The DDR4 spec defines memory that operates on 1.2V, compared with DDR3's 1.5V and 1.35V low-voltage spec. According to Samsung, its DDR4 RDIMMs consume about 40 percent less power than DDR3 memory modules operating at 1.35V. We're not sure what math they used to arrive at that finding, but in a world increasingly mindful of power consumption and rising energy costs, 1.2V is better than 1.35V.
More, Wider Memory
While DDR3 supported DIMM sizes between 512 MB and 8 GB in as many as eight banks, DDR4 quadruples memory top-end by doubling the module maximum to 16 GB (with a 2-GB minimum) in as many as 16 banks. That's math we can handle. What's more, DDR4 can arrange memory banks into as many as four groups, providing faster burst access to memory and separate read, write, activation and refresh operations for each group.
Incidentally, memory speeds of DDR4 will start at 1,600MHz and balloon to 3,200MHz. DDR3 mobiles are available mostly at frequencies between 800MHz and 1,600MHz, although the spec supports 1,866MHz and 2,133MHz memory, according to a comparison chart published by memory maker Micron.