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IT’s no ‘flash’ in the pan

Flash may be the preferred solution for PC and mobile memory needs

Solid advantage: Flash storage as a replacement for the hard drive in portable PC’s may hit 128 GB by year end. For India, 2008 is shaping up as the year of ultra mobile personal computing (UMPC). Consider the quick succession of launches in the UMPC space: Intel’s Classmate PC is now on offer in the avatar of the HCL MiLeapX. Allied Computers has launched the Ethos UMPC, while Asus has brought its EeePC to India. Storage medium

All these machines sport a screen size of just 7 inches or smaller — but there is another feature they share: All three product families have jettisoned the hard disk drive as a storage medium for a much more rugged, solid state drive based on reusable, non volatile (that is it retains the data even when power is switched off) Flash memory.

Last week, Sanjay Mehrotra, co-founder (with Eli Harari), President and Chief Operating Officer of the California-based Sandisk Corporation, a market leader in the Flash memory business and the company that invented the Flash storage card and Flash USB drive, was in Bangalore.

He showed me a solid state drive for portable computers, just 5 mm thick and weighing 40 grams. It could store 64 GB of data and was lighter by a third than a hard drive of similar capacity.

By June this year, 72 GB models will be available, he assured me and by year-end he expected SanDisk to be offering 128 GB versions. Admittedly, this comes at a stiffer price compared to hard disk drives. But that is how technology works in this business… high prices till demand for volumes build up.

System boot

SanDisk is not waiting for this to happen. For PC manufacturers who would like to give their customers the best of both worlds, the company recently launched the Vaulter disk, a flash-based module that speeds up system boot up, application load-up and retrieval of files while it works in conjunction with a hard drive that performs other storage functions.

The two drives operate in parallel, increasing the overall speed and efficiency of the PC or laptop.

In addition to the ubiquitous USB or Universal Serial Bus drive also known as the thumb drive or memory stick, which these days can be had in India in sizes up to 16 GB for around Rs. 2,500, Flash can be found inside digital cameras, pocket PCs, hand held MP3 players or games consoles — and increasingly in mobile phones.

Small sizes

By 2011, expect to see the smallest of these — the kind that go into mobile phone slots — available in sizes of 128 GB or more, says Gavin Wu, SanDisk’s Hong Kong-based Managing Director for Asia-Pacific.

It is possible to squeeze so much data into a thumb-nail sized device because companies like SanDisk, Samsung or Toshiba have gone double or triple deck stacking the memory cells so that each of them stores 2 or 3 bits of information.

This is called a multi level cell or MLC and later this month SanDisk and Toshiba will jointly launch the world’s first 16-GB 3-bits per cell Flash chip.

It will use what is known as NAND Flash architecture — this means the cells are connected in series, resembling a NAND gate. The vast majority of commercial Flash storage modules are NAND devices — as against NOR Flash where the cells are connected in parallel like NOR logic gates.

NAND Flash reading speeds will be an order of magnitude slower than NOR Flash speeds — while writing speeds will be faster.

Consumer choice

This is acceptable for the type of applications to which Flash memory is put today and the advantage of being able to stack more NAND Flash cells into a given space has made it the mass consumer choice. But NOR Flash is not about to roll over and die. There are many applications where memory has to be written only rarely, but read very often and very fast — like the BIOS settings in a PC.

And soon after Dr Fujio Masuoka of Toshiba announced his invention of Flash Memory in1984, Intel saw the huge potential of NOR Flash as a substitute for that older Ready Only Memory or ROM chip and invested heavily in the technology.

Long time partner

Why are we telling these old stories today? Because earlier this month, Intel finally hived off all its technology in (mostly) NOR Flash, and joined hands with long time partner ST Microelectronics and created a new company called Numonyx, headquartered in Switzerland.

The new entity will harness the fruits of their joint innovation in creating memory by an entirely new process, that is already exciting semiconductor material scientists: It is called PCM or Phase Change Memory and might well be the first big breakthrough in NOR Flash for almost 30 years.

Crystalline structures

In PCM, the microscopic bit is heated to anything up to 600 degrees celsius; this melts the bit which when cooled solidifies into one of two crystalline structures which represent a one or a zero.

Sounds complicated? Yes; but the reward is that PCM can sustain tens of millions instead of tens of thousands of read-write cycles compared to NAND Flash.

Reading data is as fast as NOR Flash, writing is as fast as NAND Flash — so you have a device that is the best of all existing Flash technologies.

Shrinking tolerance

So it seems the innovations in NAND Flash and PCM will continue apace for some more time to come, shrinking the manufacturing tolerance to 45 nanometres and beyond, squeezing more and more cells on every square cm. of substrate till a gigabyte will reduce to a dot, invisible to the naked eye.

Players like Intel and SanDisk are harnessing the efforts of their India-based engineers in this quest. Flash is clearly the way memory is going these days — and that’s no flash in the pan!