The Raspberry Pi’s $25 “Model A” made a brief appearance this week on the website of Allied Electronics, its U.S. distributor. Compared to its $35 sibling, the lower end Linux-fired SBC (single board computer) sports half the RAM, one USB port instead of two, and lacks an Ethernet spigot.
It’s unclear when (or whether) additional low-end models will become available, based on a statement on Allied’s website, saying: “Due to limited supply of the Raspberry Pi Model A, we are not offering preorders or backorders on the product at this time. The Raspberry Pi Model A will only be available for purchase when we have inventory on hand to fill the order.”
Although Allied also shows the $35 Model B as being out of stock, the distributor is currently accepting preorders for that model, with the caveat that “delivery times will vary and may exceed 6 weeks.”
Model A vs Model B
The photos below show the two Raspberry Pi models.
Raspberry Pi models A (left) and B (right)
(click images to enlarge)
The table below compares the features of the two models.
|Model A||Model B|
|Chipset||Broadcom BCM2835 (CPU + GPU)|
|GPU||Broadcom VideoCore IV|
|Memory||256MB SDRAM||512MB SDRAM|
|Video out||HDMI; composite RCA|
|Audio out||HDMI; 3.5mm analog out|
|Audio in||via USB mic or ext. sound card|
|Onboard storage||SD/MMC/SDIO slot|
|Network interface||None||10/100 Ethernet|
|USB 2.0 ports||1||2|
|Other I/O||UART, GPIO, SPI, I2C, I2S|
|Power||5VDC @ 500 mA||5VDC @ 700 mA|
|Size||85 x 56 mm|
What’s on the board
As indicated in the table, the Raspberry Pi is based on a Broadcom BCM2835 system-on-chip (SOC) processor. Broadcom describes the BCM2835 as “a cost-optimized, full HD, multimedia applications processor for advanced mobile and embedded applications that require the highest levels of multimedia performance.”
In addition to an ARM1176JZ-F applications processor, the BCM2835 integrates a dual core VideoCore IV graphics acceleration subsystem, which Broadcom says offers…
- 1080p30 Full HD HP H.264 video encode/decode
- Advanced Image Sensor Pipeline (ISP) for up to 20-megapixel cameras operating at up to 220 megapixels per second
- Low power, high performance OpenGL-ES 1.1/2.0 VideoCore GPU with up to 1 Gigapixel per second fill rate.
- High performance display outputs supporting simultaneous high-res LCD and HDMI with HDCP at 1080p60
As seen in its photos (above), the Raspberry Pi SBC contains little more than the BCM3835 SOC and some support circuitry. The drawings below show more of what’s on the SBC, and what’s supported externally.
Raspberry Pi connectors and connections
(click each image to enlarge)
Further details on the Raspberry Pi SBC are available on the project’s website. Additionally, eLinux.org’s embedded Linux wiki provides extensive technical information relating to all aspects of the Linux-powered SBC, here: hardware; software.