The Raspberry Pi is available in several editions: the model A and the model B are most popular. Named for the differing editions of the classic BBC Micro from British computing giant Acorn. The main differences from these two models is that the model B has a 10/100M Ethernet jack and two USB ports to the A's single port and lack of any form of on-board networking.
This is the Raspberry Pi Model B with 512MB RAM. At it's heart a Broadcom BCM2835 system-on-chip processor running at 700MHz, with a VideoCore IV GPU running at 250MHz. A single 256MB module of Hynix LPDDR memory running at 400MHz provides RAM for both the CPU and GPU, with the typical split leaving around 186MB of memory available for the user.
If you're wondering why you can't see the Broadcom SoC anywhere on the Raspberry Pi, it's because you're looking in the wrong place. The processor is hidden beneath the Hynix memory chip at the centre of the board, which uses a package-on-package (PoP) mounting process to create a RAM-SoC sandwich.
Connectors around every edge of the board provide input, in the form of a microUSB power socket and two USB 2.0 ports, and output with HDMI, 3.5mm audio and RCA composite video all present and correct. For those looking to use the board in an embedded environment, there's also a Display Serial Interconnect (DSI) connector for flat-panel displays and - exclusive to the Model B - a MIPI camera connector.
The underside of the board is pretty barren, with nothing much to see but a collection of surface-mount resistors, capacitors and a couple of crystals. The sole exception is the SD card slot, which provides the Raspberry Pi with its only form of on-device storage. While basic, the connector serves its purpose - although if you're thinking of building a case, it's worth mentioning that the SD card sticks out around 17mm beyond the edge of the board.
This, plus a proud-sitting pair of USB ports and the RCA jack, gives the Pi an overall size of around 109mm x 63mm. With the 'official' size of the board - measured purely in terms of the area of the PCB - being 85.60mm x 53.98mm, that's a significant extra bit of space for box-builders to find.
Broadcom BCM2835 SoC
700 MHz ARM1176JZF-S core CPU
Broadcom VideoCore IV GPU
512 MB RAM
2 x USB2.0 Ports
Video Out via Composite (PAL and NTSC), HDMI or Raw LCD (DSI)
Audio Out via 3.5mm Jack or Audio over HDMI
10/100 Ethernet (RJ45)
8 x GPIO
SPI bus with two chip selects
Power Requirements: 5V @ 700 mA via MicroUSB or GPIO Header
Supports Debian GNU/Linux, Fedora, Arch Linux, RISC OS and More!