Key difference between DDR4 and DDR3 RAM

ddr3 slot   Dan ddr3 in ddr4 slot

Can I use both in the same computer? Your system is only compatible with DDR4 memory The layout of the pins on a DDR3 modules are

Socket LGA 775; Supported Intel Core 2 QuadCore 2 DuoPentium Dual-Core Supported 2 DIMM of DDR3 13331066800MHz; Supports BIO-Remote 2 Technology  They don't even fit in the same slots There were a very few motherboards that had DDR4 and DDR3 slots, but you could only use one or the other

terminator 2 slot review Xllbyte New Sealed SODIMM DDR2 2GB Memory for Laptop RAM 533mhz · Kllisre DDR3 DDR4 8GB 4GB 16GB Laptop Ram 1333 1600 2400 2666 3200 DDR3L 204pin 2-Slot Thermal and Power Specs Maximum GPU Temperature 94 Maximum Graphics Card Power 120 W Minimum System Power Requirement 400 W