Thanks for the memories

Excitement has returned to the PC market, despite lower than expected growth in sales of tablet PCs in 2011. The ultrabook concept, originated by Apple with the Macbook Air, has now been adopted and developed by Intel, through standards that a PC must meet in order to qualify for the popular moniker.
The drive for slimmer and lighter has, of course, always been there. But it is the smartphone-like instant–on capabilities, touch screens, voice recognition and all-day battery life of ultrabooks that are invigorating PC customer interest. Notably, Intel created the ultrabook category last year when it announced a $300 million fund to support the necessary hardware and software innovations that would enable all ultrabooks to meet its strict criteria, amongst which is the crucial metric of ‘18mm thick (0.70in) or thinner’. Other key criteria deal with size, weight, responsiveness and performance.

Whilst the release of Windows 8 this year will enable many classic ultrabook features, it is the OEM’s choice of memory that may largely determine how well an ultrabook is realised. With light weight, long battery life and fast boot-up times at the top of the list of must-haves, ultrabooks need good capacity, lightweight memory in a greater number of shapes and heights than before.

To tackle the fast boot-up times, the consensus so far has been to integrate a cache SSD alongside a hard drive. Notes an IHS iSuppli Storage Space Market Brief: ‘…booming sales of ultrabooks spurred by strong support from Intel Corp. will drive explosive growth in the market for cache solid state drives (SSDs) in the coming years, with shipments set to soar more than a hundredfold by the end of 2015, up from less than one million units in 2011.’

Less expensive than a standard SSD, today’s cache SSDs are made out of NAND flash — many are still based on SATA II technology as opposed to SATA 6Gbit/s — and bring speed, capacity and durability (by virtue of having no moving parts) to the ultrabook picture.

According to the IHS report, another way that ultrabooks are driving memory developments is through a rival to cache SSD, the hybrid hard disk drive. Looking like a regular hard disk drive, this uses embedded NAND as a cache on top of the usual DRAM cache. Designed primarily to cut cost from the BOM, the hybrid hard disk drive offers a combination of small capacity solid state drive for the operating system and a traditional hard drive for everything else. Not as fast as SSDs, the latest hybrid hard disks do, however, offer more capacity than a typical SSD.

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Handy NAND
Taking a bird’s eye view, the ultrabook phenomenon has already led to a shift in certain battery technology’s fortunes with ‘heads, NAND is winning; tails, DRAM is losing’ being the story so far. iSuppli forecasts that ultrabooks will push total NAND consumption in the PC sector to more than 15% of total NAND flash supply, with SSDs accounting for 3.3 billion gigabytes of NAND flash this year, up from 1.7 billion gigabytes in 2011.

Whilst the ultrabook concept may not be revolutionising NAND flash, as tiny form factors have been in design and production for several years now, there’s still plenty being done by NAND manufacturers to capitalise on the ultrabook trend. Indicative of what’s going on is Micron’s just-launched caseless mSATA 6Gbit/s high performance drive. The new C400 mSATA SSD is an ultra-lightweight, small footprint, low-power design that is said to deliver the same performance per capacity as Micron’s standard 1.8 and 2.5in C400 SSDs. Available in capacities from 32Gbyte to 256Gbyte, it is manufactured using Micron’s 25nm MLC NAND technology.

Discussing the case for SSDs in general, Ben Thiel, senior product marketing manager of client SSD for Micron Technology says: “The new ultrabook platforms are really centered on attributes that an SSD helps enable, including better responsiveness, portability, and mobility. For best-in-class ultrabooks, we are seeing the SSD as the primary storage (128Gbyte and above). With the SSD-only approach the user will get the best possible experience. The dual-drive option, whereby a smaller-capacity SSD works as a cache in tandem with a hard disk drive, provides an incremental advantage, but doesn’t rival the performance of a stand-alone SSD. For example, our 32Gbyte drive coupled with a 7200RPM HDD provides for a PC Mark Vantage score of ~24K. Our 128Gbyte drive provides PC Mark scores up to 65K.”
The appeal of SSDs will be a revolution to some. Notes Thiel: “You’ll see a greater portion of the ‘non-technical’ audience begin to experience the noticeable performance advantages of SSD computing; those are users who won’t want to go back to a hard drive.”

Dipping into DRAM
For DRAM, the market research company concludes that the future is less rosy than it has been, with report author Mike Howard and principal analyst for DRAM and memory at IHS saying: “Clearly, the era of PC DRAM growth of around 40 percent is a thing of the past.” He adds: “Ultrabooks currently use a maximum of 4Gbyte of DRAM, and we believe the emphasis on form factor with minimal size and weight will lead to ultrabooks using less DRAM on average than traditional notebooks. As ultrabook sales surge during the next four years, this will slow the growth of average DRAM usage in notebooks.”
Though DRAM’s star may be waning in PCs, there are signs of a fight back in this area. Micron for example, which produces DRAM as well as NAND, has also optimised its DRAM line to cater to ultrabooks. Micron recently launched 2 and 4Gbit DDR3Lm products that reduce standby power consumption by focusing on low self-refresh power. Notes Thiel: “Smartphone-like always-on, always-connected usage models will become standard in ultrathin notebooks and so stand-by time will be an increasingly important feature for these applications.”



Until now, most ultrabooks have used DRAM soldered directly to the motherboard to get around the form-factor issues. However, this isn’t as practical as having pluggable memory modules that can be installed just prior to shipping, or indeed, easily replaced by the end user. Also, the requirement for high-speed operation (DDR13333 +) means that relatively high cost HDI (type 4) PCB technology has to be used for the SO-DIMMs — the standard DRAM packaging for PCs. Recognising these problems, Invensas has created ‘DIMM in a Package’ technology to provide the functionality of a SO-DIMM in an ultrabook-tailored package. Explains Richard Crisp, vice president and chief technologist of Invensas: “We have developed a method for placing multiple DRAM die in the same package in a novel way. The result is that within a typical quad face down package of 16 x 16 x 1mm, we have the entire functionality of a single-sided 1 or 2Gbit SO-DIMM.”

Invensas’ DIMM in a package offers numerous advantages over SO-DIMMs, according to Crisp: “Firstly, it’s considerably smaller and so helps with the goal of miniaturising motherboard size, allowing for a bigger battery. Secondly, the design of the terminal signal assignments is simple and efficient from a circuit layout point of view. At the heart of what we have done is to symmetrically arrange the signal terminals so that the signals pass straight through the board and connect with the other device when packages are mounted on opposite sides of the PCB, in a clamshell arrangement. This reduces the complexity of the board design and means that it may be possible to reduce the number of layers, though this has not yet been proven.”

With economic conditions continuing to reduce consumer buying power, cost will ultimately be a major issue for ultrabooks, with manufacturers looking at every possibility to cut cost per system. There are likely to be many budget versions competing for attention. Indeed, the trend has already commenced with HP’s recently launched ‘Sleekbooks’, which boast similar features to ultrabooks, but cost considerably less.

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Crisp claims that the DIMM in a package will allow OEMs to achieve high-speed operation on a standard low-cost PCB to maximise the cost/performance ratio. Another reason why the new package could appeal from a manufacturing point of view is because the same footprint supports multi-die LPDDR3 and GDDR5 configurations. In this way, the OEM can use a common PCB design to build products with different memory technologies, such as DDR3, DDR4, GDDR5 and LPDDR3. The common footprint means that the test infrastructure can be shared between device types, potentially saving millions of dollars in manufacturing tooling investment.

Aside from cost, the availability of off-PC storage in the form of cloud computing could be the biggest game changer for not just DRAM, but ultrabook memory in general. It is, after all, no coincidence that Acer launched an ultrabook and its AcerCloud cloud service at the same time. For this reason, the most popular memory format is likely to end up as a hybrid in every sense of the word, whether this means pairing flash memory with a traditional hard drive or pairing a full SSD with increasingly popular cloud computing services. So whilst ultrabooks may not yet be revolutionising memory technology per say, they are likely to give cloud computing — a truly revolutionary idea — just the boost it needs.