The Raspberry Pi project has squeezed a bit more juice out of the world’s greatest educational and hobbyist computing platform, producing a new Model A+ that shadows improvements made in the Model B+ announced in July.

The Model A+ uses the same Broadcom BCM2835 system on a chip (SoC) as the Model A but brings the improvements of Model B+ to the Model A which has only 256MB of RAM (which stays the same on the A+). The most important of these is probably its smaller size, reducing the length from 86mm to 65mm.

On that theme the board now uses a Micro SD card instead if its full-size cousin and the USB ports now sit flush with the edge of the board rather than hanging slightly over it.  The audio port has also shrunk slightly with analogue sound quality available through it said to have improved.

Despite this slimming, the number of USB ports has doubled from two to four (making it easier to plug in devices without having to use a USB hub), and the GPIO connector has actually increased from 26 to 40 PINs to give more space for plugging in external devices.

A small but significant improvement is that the new design consumes around 0.5-1.0 watts less than the old one, which doesn’t sound like much but makes it easier to use the board with projects based on batteries. It also adds a little more power for connected USB devices.

The team has also added four mounting holes on the board to make it easier to attach to external cases. Perhaps the biggest news is that the Model B+ is cheaper, and will retail for $20 (£20), instead of $25 (£25).

“When we announced Raspberry Pi back in 2011, the idea of producing an “ARM GNU/Linux box for $25″ seemed ambitious, so it’s pretty mind-bending to be able to knock another $5 off the cost,” said Raspberry Pi co-founder, Eben Upton.

Given that the A+ is basically the B+ but with less memory, is the news that big a deal? In conventional computing terms no, but the Raspberry Pi is a unique example of a computer that is evolving to meet the needs of its user base rather than the marketing department.

The Raspberry Pi is intended as a platform for a huge array of programming and device projects and so things that would be incidental to most computers – PIN-outs, size, mounting holes, flush USB ports – are absolutely critical in making that easier to do.

IT has numerous imitators but none that have captured that relentless and singular vision of not being an end in itself so much as a beginning.  It’s one that explains why it has sold over 3 million units and will almost certainly double that at some point.

The Model A and B are not being replaced by the smaller A+ and B+ - Eben Upton said his team didn't want to "orphan" developers who had built designs using this form factor. "As long as there's demand."