This question about Package-on-Package RAM/CPU got me curious: My rPi B has the Samsung RAM packaged on top of the Broadcom (as I can read the Samsung product details off of the package). My rPi 2 B has the Broadcom on top of the RAM (as I can read the Broadcom product details off of the package). Is there a reason why the stacking order is different between versions, or is it different from batch-to-batch?
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The RAM on the Raspberry Pi 2 is not underneath the Broadcom chip, it's on the underside of the Pi.
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PoP limited the memory to 500M because this was the largest package available. – Milliways May 7 '15 at 23:28
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AIUI the reason for moving the memory to the bottom of the board is that the processor die was too big to fit in the PoP package. – Peter Green Jul 8 '16 at 23:07