Last week the Linley conference on mobile and wearables started with an overview and keynote address by the event’s namesake Linley Gwennap. His talk offered a few surprises and was informative all around. As you have seen recently reported here on SemiWiki, he sees smartphone shipments continuing to rise, but with a declining growth rate. With penetration of smartphone handsets reaching 69% it is bound to level off. Nevertheless, there are estimated to have been 1.95 billion smartphones shipped by 2020.
However, even in the face of this growth there has been significant consolidation. Hopefully this is mostly over by now, but we have seen Intel, Marvell and Broadcom exit the mobile processor space, leaving just 3 big players – Qualcomm, MediaTek and Spreadtrum. At the same time a number of companies are opting to become verticals, and develop their own – Apple, Samsung and Huawei. Samsung and Huawei are also making their own cellular modems.
While we’ve seen Qualcomm lose some its luster over the last couple of years, they are still holding their own, owing in part to their use in high end phones, such as the Galaxy S7. The other three players are gaining on Qualcomm. Linley believes that the LTE price wars favor MediaTek. Spreadtrum is making its gains through the growth of low end smartphones.
Most processor chip vendors in the smartphone market opt to license specific component IP such as CPU, GPU and others for their SOC’s. There are some larger players who can afford and choose to develop their own IP. But this option is limited to only the top players in the market. Linley lists MediaTek, Spreadtrum, Rockchip and Allwinner as examples of houses that use all standard IP blocks. The players that use all standard IP, with the exception of one key IP element are Samsung, Apple and Huawei. In the last column we see Qualcomm and Intel incorporating most or all of their own IP in their processors.
Linley also spoke about the design issues revolving around the optimal number and size of processor cores. So called Big.Little designs use 8 or more cores, with half being larger cores and the other half being smaller cores. The larger number of big cores can create a dark silicon problem because they may generate too much heat. Linley believes that a 2+4 configuration with two large processors is a good tradeoff design for mainstream applications. It offers nearly double single thread performance relative to using all small cores. It also has the advantage of consuming much less die area. However, this configuration suffers in the market from the OEMs’ fixations on 8 as a magic number of cores. Alternatively, there are configurations that use 8 small cores. This layout runs much cooler and does well on benchmarks, but not surprisingly yields much lower single thread performance.
The larger displays found on newer smartphones are driving the need for more GPU cores. We are seeing resolutions in the range of 4-8 Mpixel. In the iPad Pro, which uses the AX9, there are 12 GPU cores. Adding more GPU’s allows the main processor to run at a lower clock rate, thus reducing power consumption. Another optimization to accommodate the higher bandwidth is the addition of wide buses. The AX9 uses a 128-bit DRAM bus to achieve 51GB/s.
Another significant change for GPU’s is the addition of shared virtual memory in OpenCL 2.0. No longer does data need to be copied between CPU memory and GPU memory. Cache coherency is becoming a critical asset for system performance. Linley pointed to ARM’s Mali-G71 as the first cache coherent GPU. Both Arteris and NetSpeed have offerings for Network on Chip interconnect supporting cache coherency that in turn provides the highest benefit for shared memory between GPU’s and CPU’s.
As no surprise Linley touched upon mobile security concerns during his keynote. Smartphones are a target rich environment for hackers. They contain a lot of attractive sensitive data: contacts, passwords, financial information, etc. Solving the security challenges for smartphones calls for both a hardware and software solution. On the hardware side secure boot, secure storage and advanced encryption are all necessary. Then the software must make full use of these features. The addition of biometric sensors can help reduce the likelihood of unauthorized access. Regardless, security will remain a very important issue in the mobile space for quite some time.
Stepping back from the handset side, Linley went on to discuss the progress in LTE. Carrier aggregation is now used across all tiers. This allows the combination of different bands to carry one data stream. In doing so, it linearly increases bandwidth. Within LTE we are seeing Category 9/10 data rates of up to 450 Mbps implemented at the high end. Later this year we can look for the first shipments of handsets with Category 16. This will bring data rates up to 1.0 Gbps – truly impressive for wireless. This is accomplished by using QAM256 and by taking advantage of unlicensed spectrum. The ability to add unlicensed spectrum means that more carriers will be able to offer gigabit data rates, even if they have limited licensed spectrum.
So where are we on 5G? Well, it’s on its way, and in some ways sooner than expected. Despite the formal plans to roll out 5G in 2020, some carriers like Verizon are looking at a selective launch of 5G as early as 2017. With 5G will come the use of new bands for higher data rates, increased carrier aggregation, and multiple simultaneous connections over multiple signals – such as small cell and macro cell and even WiFi. Verizon will probably pick a subset of the 5G technologies and leverage new signal bands to boost data rates. But with their “5G” roll out will come confusion about what 5G really is, similar to what happened when 4G rolled out early with features not compliant with the formal specification.
The second half of Linley’s talk covered wearables. Space does not permit going into that in this article. Overall the conference was very informative. The sessions in the two day conference delved much deeper into key issues such as security, on chip networks, hardware architecture, etc. For more information on upcoming Linley conferences follow this link.