A lot of people wondered why the iPhone 4 came out with a three-axis gyroscope, while the iPad — which was in development at the same time — did not.
The answer? Apple may have, in fact, originally considered a gyro for the iPad. That's the conclusion of Steve Bitton, a product manager at UBM TechInsights, after he took apart an iPad and discovered a vacant 24-pad slot on the motherboard, right next to the unit's STMicro STM33DH accelerometer.
That same accelerometer eventually wound up in the i4, along with an STMicro L3G4200D gyro. Now, the L3G4200D has a sixteen-pin form factor — but another gyro, made by InvenSense, would fit in a 24-pad slot. And when Bitton traced the signal paths from the iPhone 4's A4 CPU to its gyro chip, then compared to the paths between the iPad's A4 and the empty slot, they were almost identical. This led him to theorized that (a) the original iPad considered, then rejected, the inclusion of a gyro — and future iPads are likely to adopt the same L3G4200D gyro as the i4.
[Via 9 to 5 Mac]