A user already has 2 RAM modules in a 64-bit Windows 7 PC. Each is a 1GB DDR-PC1600 RAM module. The user has 2 additional RAM modules that are each 2GB DDR-PC800. Which of the following is true…

Question

Options

• AThe system only accesses the pair of 2GB RAM modules
• BThe system accesses all RAM at 100MHz
• CThe system enables ECC on all RAM modules
• DThe system will not work as all RAM has to be equal sizes

• A
  3% (1)
• B
  83% (24)
• C
  10% (3)
• D
  3% (1)

Explanation

When RAM modules of different speeds are mixed in a system, the motherboard defaults to the speed of the slowest installed module to ensure stability. DDR-PC1600 operates at an effective 200MHz (100MHz bus × 2 for double data rate), while DDR-PC800 operates at an effective 100MHz (50MHz bus × 2). Since PC800 is the slower module, all four modules will run at 100MHz - making B correct. The system does not disable the slower or faster pair (A is wrong), ECC is a separate error-correction feature not automatically enabled by mixing speeds (C is wrong), and modern systems handle mixed-size RAM fine (D is wrong).

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