Alpha boards in manufacture

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Raspberry Pi

July 25, 2011

Over the past three months, we’ve been working hard to finalize the specs for the Raspberry Pi device, and to produce schematics and a PCB layout. Last Tuesday, we sent an alpha release of the board for manufacture. From an electrical perspective, this board is intended to be identical to the final device; the resulting units will be used to validate the schematic design, and will serve as our interim software development platform.

Raspberry Pi alpha PCB

Key differences between the alpha and final boards are:

The alpha board is roughly 20% larger than the credit-card-sized final board. As you can see, our size is already dominated by the area of the various connectors.
The alpha board has six layers rather than four, and uses a variety of expensive HDI features (blind and buried vias, via-in-pad) which we wish to eliminate from the final board.
The alpha board has various test and debug features which will not be present on the final board.

The ICs used in the design are an ARM-based application processor (center) and an SMSC LAN9512 USB 2.0 hub and 10/100 Ethernet controller (right and down from center). The SDRAM is mounted on top of the application processor in a PoP configuration.

Following the example of the BBC Micro [ http://en.wikipedia.org/wiki/BBC_Micro ], we intend to launch both a Model A device (lacking the LAN9512, and with 128MB of RAM) at the $25 price point, and a Model B device (including the LAN9512, and with 256MB of RAM) for a $5-10 additional cost. We remain confident of shipping before the end of 2011.

Check back in a couple of weeks to see how the alpha boards turned out.