Question

why notch position of DDR2 is different from DDR4?​

Answer 1

Answer:

What is DDR4?

Double data rate fourth generation (DDR4) is a memory standard designed as a better, faster, more reliable replacement for DDR3.

How does DDR4 differ from DDR3 in appearance?

Physically, a DDR4 module, or dual in-line memory module (DIMM), looks very similar to a DDR3 DIMM. However, DDR4 has 288 pins compared with DDR3’s 240 pins; DDR4 SO-DIMMS have 260 pins instead of 204 in DDR3. The DDR4 key notch is in a different place, and the edge connector looks like a slightly curved “V” to facilitate insertion. This design also lowers insertion force, as not all pins are engaged at the same time during module insertion.