Why does a socket that can support DDR3 or DDR4 need to be different from a socket that only supports DDR3?
And with the current socket being 1700, they're going to change it again for the next generation to 1851, and with a quick look I don't see any feature changes that are motivating the change. (Upgrading 4 of the PCIe lanes to match the speed of the other 16 definitely does not count as something that motivates a socket change.)
So by my reckoning, half their desktop socket changes in the last decade have been unnecessary.
Because DDR4 is electrically different and memory controllers are all on-die.
Intel could get away with doing that pre-Nehalem because the memory was connected via the northbridge and not directly (which is what AMD was doing at the time; their CPUs outperformed Intel's partially due to that), so the CPU could be memory-agnostic.
AMD would later need to switch to a new socket to run DDR3 RAM, but that socket was physically compatible with AM2 (AM3 CPUs would have both DDR2 and DDR3 memory controllers and switch depending on which memory they were paired with; AM3+ CPUs would do away with that though).
There were some benefits to doing that; the last time Intel realized them was in 2001 when RD-RAM turned out to be a dead-end. Socket 423 processors would ultimately prove compatible with RDRAM, SDRAM, and DDR SDRAM.
> Because DDR4 is electrically different and memory controllers are all on-die.
Them being on-die is exactly why you don't need a socket change to take full advantage of DDR4, since they directly showed a socket can support both at once. Unless you're particularly worried about people trying to buy a new motherboard for their existing CPU, but who does that? You can tell them no without blocking CPU upgrades for everyone else.
> pre-Nehalem
> AM3 CPUs would have both DDR2 and DDR3 memory controllers
And with the current socket being 1700, they're going to change it again for the next generation to 1851, and with a quick look I don't see any feature changes that are motivating the change. (Upgrading 4 of the PCIe lanes to match the speed of the other 16 definitely does not count as something that motivates a socket change.)
So by my reckoning, half their desktop socket changes in the last decade have been unnecessary.