Written by Frank Ferro
I recently spent four busy days at a tradeshow where I was fortunate enough to get a couple of nice gifts – and perhaps by coincidence, these items are a good representation of where we are in the high-tech market today. Let me explain. As I write this blog, I’m wearing my new fitness-tracking device that I received as part of the ARM IP Connected Community challenge at the Design Automation Conference (DAC) back in early June (I lost the challenge, by the way). The device is fun, tracks my activity, displaying it on my mobile phone – AND reminds me that I am not getting enough exercise or sleep (not so fun). Another gift I received was a battery pack that can recharge my cell phone several times in between plug in opportunities (usually every night). Don’t get me wrong, this was a nice gift, however it hit me that while IoT seems to be the trendy topic, less often is it mentioned that our smartphones can’t get through one day without being recharged! A product like a battery pack would not be necessary if our mobile phones could last a few days on a single charge.
It seems to me that we are caught between two markets. IoT certainly deserves our attention and investment, but is several years away from delivering on the ‘billons of units’ potential. And I’m not sure that IoT – the Internet of Things – shouldn’t be IoT – the Infrastructure of Things. Mobile phones and wearables are the things the IoT connects, right? I digress. As much as IoT is a hot topic (and again, it should be) at the same time we shouldn’t ignore the nearly two billion-unit mobile phone market that is filling up our fabs and currently “paying the bills”. As interesting as it is to talk about IoT, we also need to look at and innovate on ways to lower power and costs for our existing and future mobile devices. Not to mention these resulting innovations will eventually benefit IoT products and other connected devices where power and cost pressure will be even greater.
Today, when it comes to power consumption, SoC designers for the mobile market have been ‘treading water’ given that the processor speeds and memory bandwidth have increase by about 10x. At the same time, they contend with power requirements that remain relatively unchanged, including the power density of the IC, thermal envelope, and battery size (see our white paper on “Implementation Challenges and Solutions for High Performance, Low Power Memory Systems”).
To help improve battery life and reduce cost in today’s mobile devices, we at Rambus are focusing on signaling techniques that can save power in the memory subsystem – which frequently consumes a lot of power depending on the application(s) being used. To achieve further power savings, a SoC manufacture’s only option (so it seems) is to move from DDR3 to DDR4 for their main memory. They do this because DDR4 saves power, but it also adds cost to the overall system.
One alternative to moving to DDR4 that Rambus is offering SoC developers is the ability to use LVST (low-voltage swing termination) signaling with their current DDR3 designs. LVST signaling, when used in conjunction with DDR3 DRAM that supports this signaling, can achieve significant power savings – up to 25% in the overall memory subsystem (for a detailed discussion on this topic see the Rambus SemiEngineering blog: Memory Matters for Mid-Range Mobile Devices). In addition to saving power, staying with DDR3 DRAM saves development costs associated with switching to DDR4 DRAM and, of course, we expect the price of DDR3 will remain lower than DDR4 for at least the next few years. Sticking with DDR3 DRAM is a great alternative for today’s SoC manufacturers, especially in the growing mid-range smartphone market where cost is critical.
My two freebies identify the dichotomy between where we are (the need for the extra battery pack) and where we are focused (IoT fitness trackers). The practical side of me is happy to have a device that extends the battery life of my phone. But the engineer in me wants to know why we such an accessory is still needed. The less practical side of me likes my new toy, the fitness tracker – now if only it would stop telling me to exercise more!