Tear Down: Microsoft re-tunes the Zune
On the outside, it looks a lot like an iPod and acts a lot like an iPod, performing the same functions as an iPod. But peel back the cover and Microsoft's Zune reveals it's not an iPod; Microsoft has gone to great lengths to configure the Zune in their own image.
The first-generation Zune, designed in partnership with Toshiba, on the inside at least, looked a lot like Toshiba's own player. The second-generation player was defined from scratch by Microsoft, including all the hardware, software, and mechanics.
Microsoft did a good job specifying exactly what they were looking for and not settling for anything less. The Zune is designed with an easy-to-use touch sensor, a 1.8-inch color display, and a WiFi connection. And all those features are packed into about 3.5 by 1.5 inches, a feat Microsoft achieved through an innovative board design that also left room for the battery.
The model that I took apart was powered by a Freescale i.MX32 microprocessor, as shown in Figure 1. While this series of microprocessors is in the Freescale general catalog, this particular version is not available on the open market. It's only available to special high-volume customers.
Similar to an i.MX31 (now the standard product), the i.MX32 tries to balance high performance with low power. It's designed with an ARM11 CPU core.
"For a product like the Zune that employs a feature-rich operating system like Windows CE, it's important to have a lot of headroom in terms of performance on your host processor," says Boris Bobrov, Freescale's manager of applications engineering. "That way you don't spend extra battery life for high performance."
Lots of processing power
My immediate reaction to having an ARM11 in an MP3 player was that it's overkill, and you don't want to pay for processing power that you're not using. But after further analysis, it became clear that the user interface on the Zune requires all the available performance, with its snappy, feature-rich graphics. That's one of the features of the Zune that separates it from the competition.
"It's pretty common that the requirements of the user interface drive the choice of the processor," says Dan Loop, i.MX product manager at Freescale. "Being able to browse large content libraries is something that OEMs are pushing for in this class of device."
The Zune's different subsystems operate at a variety of voltage levels. One of the nice features of the i.MX processor is that it always defaults to the lowest voltage possible for the required performance level. To ensure maximum performance, the system designers take advantage of techniques like dynamic temperature compensation, which measures the processor's temperature. Dynamic frequency scaling, depending on the CPU load, reduces the frequency, thereby reducing the voltage. The processor's main frequency operating points are 66, 132, 266, and 532 MHz.