Raspberry Pi 400: Its designer reveals more about the faster Pi 4 in the $70 PC's keyboard

Raspberry Pi designer shows off the custom PCB for the Raspberry Pi 4 inside the new $70 Pi 400 keyboard computer.
Written by Liam Tung, Contributing Writer

Raspberry Pi's designers have revealed more about the overhauled design of the Raspberry Pi 4 inside its new Raspberry Pi 400 keyboard computer.   

The new $70 Raspberry Pi 400, announced on Monday, offers fans of the Raspberry Pi single-board computer a polished, modern take on far less powerful classics from the 1980s like the BBC Micro, ZX Spectrum and Commodore Amiga.          

While the squarish Raspberry Pi 4 measures 85.6mm × 56.5mm, or 2.22 inches × 3.37 inches, the designers of the Pi 400 crafted an elongated custom printed-circuit board (PCB) to fit the Pi 400 computer keyboard's dimensions of 286mm × 122mm × 23mm, or 11.25 inches × 4.8 inches × 0.9 inches. 

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The Pi 400 shares the Pi 4's circuit layout for power management, processor, and memory. However, the designers had to reposition the GPIO connector and ports to suit the keyboard's ports, which are all located on the rear of the computer. Also, the keyboard has a dedicated USB2.0 port.  

Raspberry Pi senior principal engineer Simon Martin has posted a blog answering the questions some fans have raised about whether the Pi 400 is a left-handed device. 

The USB ports are located on the left side of the keyboard's rear, which can make a cable-connected mouse a tangly experience for right-handed users. He concedes it was a right-handed design challenge that he couldn't solve but notes it isn't a problem for right-handed users with a Bluetooth mouse. 

"The PCB shape had to be defined early on so that the industrial designers could get on with the housing design, and I then stared endlessly at the PCB layout, trying to get one of the USB ports to route to the right side without wrecking the signal integrity of the memory or the HDMI; I could not find a way to do this," writes Martin. 

While Raspberry Pi single-board computers don't come with a heatsink, the Pi 400 includes one to offset its higher 1.8GHz operating point – the Raspberry Pi 4 runs at 1.5GHz. 

"Raspberry Pi 400 contains a heat spreader that dissipates the heat across the whole unit, front and back, so that no part of it will feel too hot to touch. In fact, there is enough thermal margin to overclock it, if you're so inclined," Martin notes. 

SEE: Raspberry Pi 400 is out: $70 for a complete PC with a faster Pi 4 in a keyboard

Martin explains that the Pi 400 team didn't opt for the Raspberry Pi Compute Module – a compact variant of the board without ports for industrial applications – because it was more efficient to make a custom PCB at the scale at which the Pi 400 is being made at Sony's manufacturing facility in Wales

"With hundreds of thousands of Raspberry Pi 400 units in the first instance, we are above that scale," boasts Martin. 

Finally, the Pi 400 marks the first Raspberry Pi product with an on/off power button, albeit a two-key affair that works by pressing Fn+F10. Pressing the pair for two seconds restores power.   


The Pi 400's designers opted to create an elongated custom printed-circuit board to fit the computer's keyboard.

The Raspberry Pi Foundation

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