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Apple Inc.’s latest MacBook Pro laptops came with a number of upgrades to processor speeds, RAM and hard drives — not to mention reduced price tags.

Apple also reduced something else: the serial-ATA (SATA) drive interface, which dropped from 3Gbit/sec on earlier MacBook Pros to 1.5Gbit/sec. on newer ones.

The downgrade was initially picked up by Mac aficionados on the MacRumors.com Web site. Computerworld then confirmed the SATA change on a new 15-in. MacBook Pro as well as on the smaller, 13-in. model.

The issue has cropped up on Apple’s forums and on notebookreview.com.

It was not clear whether the SATA interface on the latest 17-in MacBook Pro or the ultra-thin MacBook Air were also revamped. Computerworld was unable to get an explanation from Apple about the change.

The move to a slower SATA interface has tech experts baffled, leading them to question whether Apple had encountered technical issues associated with the faster interface.

“I’m puzzled by it, as I know a lot of other people are. The only reason why I could think they would do it is there was some serious technical glitch — maybe the [processing] chip, maybe the optical drive,” said Tom Coughlin, founder of data storage consultancy Coughlin Associates Inc.

Coughlin said some industry rumors indicate there were issues with data transfer rates associated with the MacBook Pro’s optical drive, which has a 1.5Gbit/sec interface, “but usually the newer SATA interfaces are downward compatible with older interface products,” he added. “So I don’t even know why that would be a problem.”

Jim McGregor, chief technology strategist at market research firm In-Stat in Scottsdale, Ariz., believes Apple may have been seeing data error problems at higher I/O rates with the 3Gbit/sec SATA interface. “It may be that those were higher error rates than they preferred,” he said.

McGregor noted that the slower SATA interface will not likely affect most MacBook Pro users, as the data transfers from traditional hard drives don’t saturate a 1.5Gbit/sec SATA interface, let alone a 3Gbit/sec interface. However, users with USB hubs connecting multiple external devices — such as flash drives or a hard disk drive — to a laptop or desktop computer might saturate the 1.5Gbit/sec SATA interface, hampering I/O.

The most obvious limitation of a slower SATA interface would be to SSDs, which are more than capable of fully using a SATA 1.5Gbit interface, with many of the drives boasting 230MB/sec sequential read rates, as well as write rates above 150MB/sec.

“It really depends on how much you hit them,” McGregor said. “In many cases, the average consumer isn’t going to be tapping into that full [1.5Gbit/sec] bandwidth, but memory-hungry applications like those for gaming, digital content creation and database applications will peg it and will limit the performance of an SSD.”

Using a hard drive interface like SATA for SSDs is not optimal for for the disks, which have gained popularity for their fast read speeds, lower power use and and ability to withstand physical shocks that can harm traditional drives. SSDs cost more per gigabyte than hard drives, and are offered as pricey options on all of Apple’s MacBook Pro laptops.

Given the speed with which SSDs can move data, most original equipment manufacturers are likely to eventually embed the NAND memory chips used by the drives onto the motherboards of computers in order to take full advantage of the I/O capabilities of non-volatile flash memory.

“Storage will begin to look more like a memory module than a hard drive,” said Dean Klein, vice president of Micron Corp.’s SSD group.

Despite the hype surrounding Google Inc.’s Android operating system, Nvidia Inc. sees more immediate promise in Microsoft Corp.’s Windows CE for ARM-based netbooks.

Mike Rayfield, general manager for Nvidia’s mobile business unit, said Nvidia preferred Microsoft’s Windows CE over Android because of CE’s maturity. He said Android currently has a rough user interface.

Rayfield also plugged Nvidia CEO Jen-Hsun Huang’s prediction yesterday that Tegra, Nvidia’s System-on-Chip (SoC) for ARM hardware, could account for half of Nvidia’s revenue within a few years, while also reaping higher profit margins than Nvidia’s current products.

Rayfield was coy, however, regarding reports that say Microsoft’s upcoming Zune HD media player will use Tegra.

“Microsoft hasn’t confirmed that … so until they comment, I can’t,” he said.

For smartbooks, Nvidia is working with Microsoft to optimize Windows CE when it runs on Tegra. The counterpart to Nvidia’s Ion platform for Intel Atom-based netbooks, Tegra bundles an ARM CPU (the 750 MHz ARM 11) with specialized chips designed by Nvidia for graphics, HD video encoding and decoding, stereo sound and more.

That will allow Windows CE devices to offload much of the heavy multimedia work onto Tegra, resulting in better performance, 1080p video, and low power usage. Nvidia claims that Tegra smartbooks should allow users to listen to music for 25 days or watch HD video for 10 hours, versus 5 hours and 3 hours, respectively, for an Intel Atom netbook.

Nvidia chose to work with Windows CE first, said Rayfield, because it “is a rock-solid operating system that has been shipped billions of times.”

Windows CE also has a “low memory footprint and a good collection of apps,” Rayfield said.

He said Nvidia is also improving Tegra for use on Windows Mobile, a close variant of Windows CE, for ARM-based smartphones.

Nvidia is working with Google to accelerate Android, which is based on Linux, when running on Tegra hardware. But it will be about a year before that delivers for smartbooks, due to existing limitations in Android, he said.

For instance, Android screen icons that fit on smartphone screens (usually 4-inches and under) are oversized on a smartbook’s 8- or 9-inch screen, he said.

Also, all video and graphics rendering in Android is done today by the operating system’s Java code, a technique he says is too slow for HD video.

“There’s no hardware acceleration. It’s all software,” Rayfield said. “Everyone’s talking about Android for cell phones, but the reality doesn’t exist for the larger displays [of a smartbook.]”

A Google spokeswoman declined to respond to Rayfield’s comments about Android.

Rayfield’s comments echo those about Android by others in the emerging smartbook space. Kerry McGuire, director of strategic alliances at ARM, told Computerworld recently, “I do think that there is more work that can and will be done to bring the things we love about Android into form factors [such as netbooks.]”

Rayfield evinced even less enthusiasm for more mainstream flavors of Linux available on ARM, such as Canonical’s Ubuntu or Intel’s Moblin.

“The world soundly rejected the first netbooks that came out with Linux,” he said. “Printers didn’t work, and devices didn’t get recognized. The whole thing was a mess.”

Nvidia has garnered 42 design wins from 27 different manufacturers all building devices using Tegra, said Rayfield. More than half of the wins (26) are for smartbook or tablet designs. Those can arrive to market in just six months, versus two years for smartphones designed for telecom carriers, Rayfield said.

Rayfield echoed comments by Nvidia executives during its analyst day on Tuesday that Tegra could make up more than half of Nvidia’s sales ($3.4 billion in fiscal year ending January 2009) very soon.

“It’s an aggressive statement, no doubt. But we’ve got a pretty good pipeline,” Rayfield said. Also, it won’t be long before consumers, rather than re-ripping Blu-ray movies to watch on different devices, will expect to be able to carry a single, HD-quality version of their videos around with them for easy sharing and viewing on large-screen TVs.

By using its own graphical expertise in Tegra rather than licensing it, Nvidia hopes to reap gross profit margins of 45% on Tegra by charging commensurately for its better performance over competing platforms from Qualcomm (Snapdragon) and Freescale Semiconductor, Rayfield said.

The next generation of Tegra due early next year will boast 4 times the performance of today’s version, while the 2011 update will improve performance 10 times over today’s, he said.