Please Note. This method combats mechanical compatibility between the Raspberry Pi Model B & Model B+. Electronic compatibility is a little different, please see below.
So you've got your shiny new Raspberry Pi Model B+! Great!
But there's a problem! That 26 pin ribbon cable you had for your old Model B doesn't seem to fit :( In addition, that big breakout board you want to use doesn't fit either! The extra pair of USB ports and GPIO increase to 40 pins (which are fantastic additions and add a LOT of functionality) unfortunately do cause some issues in terms of mechanical back-compatibility with Raspberry Pi Model B boards and accessories.
A Note on Electronic Compatibility between the Raspberry Pi Model B vs Model B+
Although the majority of breakout boards will have absolutely no issues, devices that utilise I2S (such as the Wolfson Audio Card) will not work. I2S devices utilises the I2S pins next to the GPIO header - which have now been moved onto the main GPIO header. Please see the pictures below for clarification.
For a really good overview of the new Raspberry Pi Model B+ Please check Adafruit's Introduction. It covers the main differences in compatibility in addition to a detailed overview of the new unit.
Raspberry Pi Model B - I2S Pins are located adjacent to the GPIO pins:
Some breakoutboards such as the Wolfson Audio Card have additional contact pins:
So, if your Raspberry Pi breakout board features these extra I2S contact pins, it's likely it won't work with the new Raspberry Pi Model B+. The good news, is that the majority of boards don't use these pins!
An Easy Method to Make your Model B Raspberry Pi Accessories compatible with the New Model B+
So, if you've got a 26 pins ribbon cable, and don't want to chop it up, or have one of the larger 26 pin Raspberry Pi breakout boards (shaped around the USB ports) then this solution is a quick and simple fix! All you need in an Extra-Tall 26 Pin GPIO Header and it should work with just about anything!
Below we've demonstrated a mechanical incompatible breakout board (the UPiS Advanced) and an incompatible ribbon cable assembly (Adafruit Cobbler Kit)
It's really simple - Just plug your GPIO header extender in. . . .
Voila! Both kits will now work perfectly!
Take care is using "heavy" breakout boards. The extra height will add extra force due to the increased moment arm (Yes, I did Civil Engineering at Uni!), so it's more susceptible to break if you slam a force down on it. Although, in all likelihood, you'll just bend the pins on the extra tall header :)