220-1101 Question 232
Single answerDual In-line Memory Module (DIMM)A technician is upgrading a desktop PC that currently has one 8 GB DDR4 DIMM installed in slot A2. The motherboard manual states that it supports dual-channel memory and recommends using matched DIMMs in slots A2 and B2 when installing two modules. The technician adds a new 8 GB DDR4 module from a different brand, but after the upgrade the system powers on with no video and emits a memory error beep code. The original module works by itself, and the new module works by itself in slot A2. Which action is the BEST next step to restore reliable operation with both DIMMs installed?
- A
Install the two DIMMs in slots A1 and A2 so they are next to each other
- B
Replace both modules with a matched memory kit that is listed as compatible and install them in A2 and B2
- C
Mix the DDR4 DIMMs with a DDR3 module so the motherboard can fall back to a lower speed
- D
Disable dual-channel mode in BIOS and leave the modules in any two available slots
Show answer and explanation
Correct answer: B
Explanation
The key troubleshooting clue is that each DDR4 DIMM works individually, but the system fails when both are installed together. That points away from a bad motherboard slot and toward module compatibility or unsupported mixed-memory behavior. In real-world PC support, the most reliable fix is to use a matched memory kit from the same vendor and product line, with the same capacity, speed, timings, and voltage, and to install the modules in the slots specified by the motherboard documentation. Motherboard manuals commonly specify A2 and B2 first for two-DIMM dual-channel operation because those slots are optimized for signal integrity. CompTIA A+ Core 1 expects candidates to recognize proper DIMM population order, channel pairing, and the risks of mixing memory modules even when the generation and size appear to match. Vendor motherboard manuals and memory QVLs are the best references for supported DIMM configurations.
- A. Incorrect.
This is incorrect. On many motherboards, adjacent slots are not the correct pair for two-module operation. The manual specifically recommends A2 and B2 for two DIMMs. Installing memory in A1 and A2 may prevent proper channel pairing or even cause POST issues depending on the board design.
- B. Correct.
This is correct. Since each DIMM works alone but not together, the issue is likely a compatibility problem between the two modules, such as differences in timings, ranks, SPD/XMP profiles, or electrical characteristics. Best practice is to use a matched kit validated for the motherboard and install it in the manufacturer-recommended paired slots, which here are A2 and B2.
- C. Incorrect.
This is incorrect. DDR3 and DDR4 are physically and electrically incompatible. They use different keying and signaling, so a motherboard designed for DDR4 cannot use a DDR3 DIMM as a fallback option. This reflects a common misconception that all DIMM generations are interchangeable if speed is reduced.
- D. Incorrect.
This is incorrect. Consumer motherboards typically do not offer a simple setting to disable dual-channel in order to fix incompatible modules, and slot population still matters. Even if the board can run in single-channel under some conditions, using arbitrary slots does not address the root cause of incompatible or unstable mixed DIMMs.