The A4 does use this technology, but Apple certainly did not invent it (though I wouldn't be surprised if they claimed so). It has been used in cell phones for years, and only recently others are starting to adopt it, and extend it to place two chips side by side on a Si substrate within a single package. The reasons are purely economical. In the past, much benefit can be had just by shrinking the transistor size. At the current feature sizes, though, physics is not helping anymore and there is very little benefit in terms of raw transistor and wire speeds, and power. So chip makers need to find more ways to extend Moore's law a few more years. FinFETs and stacked chips are just such ways.
TSV die stacking, wire-bond die stacking, and package-on-package chip stacking are different technologies with different costs and benefits. TSV stacking allows a massive number of wires between the layers, increasing bandwidth far beyond other types of stacking; of course, this comes at very high cost.
Also, PoP stacking was used in mobile SoCs long before the A4.
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Wasn't that one of the innovations of Apple's A4 chip? Stacking the RAM chips on top of the CPU core inside the same package?
The A4 does use this technology, but Apple certainly did not invent it (though I wouldn't be surprised if they claimed so). It has been used in cell phones for years, and only recently others are starting to adopt it, and extend it to place two chips side by side on a Si substrate within a single package. The reasons are purely economical. In the past, much benefit can be had just by shrinking the transistor size. At the current feature sizes, though, physics is not helping anymore and there is very little benefit in terms of raw transistor and wire speeds, and power. So chip makers need to find more ways to extend Moore's law a few more years. FinFETs and stacked chips are just such ways.
I'm curious why my comment was downvoted? Just for future reference.
Probably the rather off-topic though I wouldn't be surprised if they claimed so part.
Ah. Makes sense. Thanks.
TSV die stacking, wire-bond die stacking, and package-on-package chip stacking are different technologies with different costs and benefits. TSV stacking allows a massive number of wires between the layers, increasing bandwidth far beyond other types of stacking; of course, this comes at very high cost.
Also, PoP stacking was used in mobile SoCs long before the A4.