In the upper right corner of the NAND flash memory is STMicroelectronics' MEMS-based accelerometer IC, used to detect the iPhone's orientation of the moment (portrait versus landscape) in order to adjust the display. Right now the function is only enabled for Web browsing, photo viewing, and iPod audio-and-video playback. As I wrote in a recent hands-on analysis, the accelerometer only reliably detects portrait-versus-landscape orientation when a user holds the iPhone at least 45° relative to the ground (and better yet nearly vertical, at ~90° to the horizontal). At the time I did my initial report, I wasn't sure if this quirk represented a fundamental sensor hardware limitation or only a cons

　　When the phone is held in front of you (vertically), gravitational forces on the accelerometer's "fingers" allow the phone to understand whether you are holding it in portrait or landscape mode. When you lay the phone on a table or hold it horizontally, gravitational forces operate uniformly around the accelerometer so it has no way of knowing where you are relative to it and can't determine whether you are trying to look at a portrait- or landscape-mode orientation.

　　Mind you, it's not a big deal; I naturally tend to cradle the iPhone cupped in my hand at waist-level, parallel to the ground, among other reasons because it requires less effort than holding the unit vertical in front of my face. In my preferred viewing position, the sensor is ineffective, but I can always temporarily raise the phone to a vertical position before rotating it, and then lower the unit again to its usual position. In fact, one could even paint this attribute as a "feature"—a sort of display-lock capability. Regardless, it's something for Apple and its accelerometer partners(s) to look at for the second-generation iPhone design.

　　Other primary ICs that also inhabit that same side of the digital PCB include a Wolfson Microelectronics audio codec (the same one as in the iPod nano, according to Semiconductor Insights) above the ARM CPU, power-management ICs from Linear Technology (below the ARM CPU) and NXP (the Apple-labeled IC in the bottom left corner of the PCB, according to Portelligent), a National Semiconductor Mobile Pixel Link transmitter between the CPU and NAND-flash chip, and a Texas Instruments LCD boost converter between the accelerometer and MPL transmitter. The digital board's other side is dominated by the SIM card connector, but it also houses a diminutive 1-Mbyte parallel-interface SST flash memory, which probably acts as the ARM CPU's boot device.

　　The iPhone's RF board is similarly jam-packed with ICs, this time concentrated on one side of the PCB (albeit with discrete components scattered across both sides). Chips you'll find on it include an Infineon GSM/EDGE RF transceiver on the right side of the PCB, a companion Skyworks power amplifier (lower-right corner), an Epcos transmit/receive duplexer (lower left corner), a Marvell 802.11b/g Wi-Fi transceiver on the left side of the PCB, a Bluetooth transceiver from Cambridge Silicon Radio just above the Skyworks IC, an Infineon cellular-baseband processor in the PCB's upper left corner, and an Intel-labeled single-package, two-die memory stack in the upper right corner of the PCB. This final device contains volatile memory and 32 Mbits of NOR flash memory. Ah yes, there's that "volatile memory" term again. As before, Semiconductor Insights says that it's SRAM, whereas Portelligent insists that it's DRAM, specifically PSRAM (self-refresh, low-power DRAM with an SRAM-like system interface).

　　For completeness, I'll wrap up by showing you some of the other images Portelligent provided (they don't have much semiconductor content, but they'll likely still be of interest to at least some of you):