TECHNOLOGY FOR CHANGE

Smarter Mobile DRAM Satisfies Need for Speed

R. Colin Johnson | Date: 04-07-11 | Comments

Dynamic random access memory holds the video, audio and other multimedia content as it plays on your smartphone or touch-screen tablet, but high-definition content is spawning the need for a speedier mobile DRAM architecture.

Battery lifetime prompts most mobile device designers to opt for the ultra-low-power versions of special mobile DRAM chips. In fact, a mass exodus is already in process to move to the second generation of these low-power (LP) double data rate (DRR) chips, with several competing efforts promising to leapfrog the LPDDR standard.

Some touch-screen tablets sacrifice battery life by using PC-style DDR1 or DDR2 memory cards, but LPDDR1 or LPDDR2 is used today by most smartphones, touch-screen tablets, digital still cameras, portable media players and portable gaming platforms.

Over the next year, according to IHS iSuppli, the latest version of mobile DRAM (LPDDR2) will come to dominate mobile devices. About 31 percent of mobile devices use LPDDR1 today, but by the end of 2011, 58 percent of new mobile device designs will have migrated to the faster LPDDR2 standard.

Chips based on the latest low power mobile DRAM standard�LPDDR2�will surpass those based on the older LPDDR1 standard during 2011. (Source: IHS iSuppli)

Mobile device makers are willing to pay a premium price for LPDDR2 because it consumes about 50 percent less power when loading a large multimedia file. However, over the next few years the size and frequency of high-definition and other large file formats are projected to increase by 10 times, prompting mobile DRAM makers worldwide to begin conjuring successors.

Today LPDDR2 achieves a data transfer rate of 8.5GB per second�an eightfold speed-up over LPDDR1. However, by 2012 IHS iSuppli claims that mobile device manufacturers will need to support data transfer rates as high as 12.8GB per second. LPDDR3 is the logical next step because it aims to double the transfer clock rate to 800MHz, in the style of DDR3. Unfortunately, that feat is not likely to be achieved until 2013 or beyond (the same time frame as DDR4)�a year behind the needs of users.

As a result, memory chip makers are scrambling to supply higher-speed DRAM architectures by 2012 that meet user expectations for escalating speeds to handle larger files. Wide I/O, for instance, promises to interconnect DRAMs inside their package for faster throughput, but is not specifically designed for mobile low-power applications. Aimed at low-power applications, on the other hand, is the Serial Port Memory Technology Consortium, which has proposed a royalty-free interface specifically that increases bandwidth by four times, at half the power, to achieve data transfer rates as high as 12.8GB per second.

Five different DRAM standards are competing to replace the current low-power (LP) double data rate (DRR) standard.

Even faster is the mobile extreme data rate (XDR) standard defined by Rambus Inc. (Los Altos, Calif.). DRAM makers will have to pay royalties�unlike open-source SPMT�but Mobile XDR is claimed to be superior by using a low-speed serial bus to probe and configure data transfers that are then made in parallel as fast as 28.8GB per second.