220-1101 Question 233
Single answerDouble Data Rate (DDR) iterationsA technician is upgrading a desktop PC used for accounting. The motherboard documentation states it supports DDR4 DIMMs only, with 288-pin slots and a maximum speed of DDR4-3200. The user purchased a discounted 16 GB DDR3 memory kit from another system and asks the technician to install it to save money. What is the BEST response?
- A
Install the DDR3 kit because DDR memory is backward compatible if the speed is lowered in BIOS
- B
Install the DDR3 kit in alternating slots so the system can run it in single-channel mode
- C
Do not install the DDR3 kit because DDR3 and DDR4 use different pin counts and keying, so the modules are not physically or electrically compatible
- D
Do not install the DDR3 kit unless the power supply is upgraded first, because DDR3 requires more wattage than DDR4
Show answer and explanation
Correct answer: C
Explanation
This question tests practical knowledge of DDR iterations in a hardware upgrade scenario. For A+ Core 1, candidates should know that DDR generations are not cross-compatible. DDR3 and DDR4 differ in pin count, notch placement, operating voltage, and chipset/motherboard support. A technician should verify memory type against the motherboard or system documentation before installation. Manufacturer motherboard specifications and system board manuals are the authoritative sources for supported RAM type, capacity, and speed. Best practice is to match the exact DDR generation required by the board rather than assuming one DDR version can substitute for another.
- A. Incorrect.
Incorrect. A common misconception is that different DDR generations work like lower-speed versions of the same standard. In reality, DDR3 and DDR4 are different memory iterations with different physical notch placement, electrical characteristics, and platform support requirements. Lowering speed in BIOS does not make DDR3 compatible with a DDR4-only motherboard.
- B. Incorrect.
Incorrect. Slot population order can affect channel mode, but it does not solve generation incompatibility. DDR3 DIMMs cannot be installed properly into DDR4 slots because the pin count and notch/keying differ. Single-channel versus dual-channel is unrelated to DDR3-to-DDR4 compatibility.
- C. Correct.
Correct. DDR3 and DDR4 are not interchangeable. Desktop DDR3 DIMMs typically use 240 pins, while desktop DDR4 DIMMs use 288 pins, and the key notch is in a different location. Motherboards are designed for a specific DDR generation, so a board that supports DDR4 DIMMs only cannot use DDR3 memory modules.
- D. Incorrect.
Incorrect. Although DDR generations differ in voltage and power characteristics, PSU capacity is not the issue in this scenario. The real problem is motherboard and module incompatibility. Even with a larger power supply, a DDR3 module would still not fit or function in a DDR4-only slot.