220-801 · Question #639
A technician has just installed two memory modules on a motherboard that supports DDR3 RAM with the bus speed up to 1600 MHz. The specifications of memory are DDR3 1066 MHz for one module and DDR3…
The correct answer is C. 1066 MHz. When DDR3 modules of different speeds are installed together, the system operates at the speed of the slowest module. With modules rated at 1066 MHz and 1333 MHz, the system will run at 1066 MHz.
Question
A technician has just installed two memory modules on a motherboard that supports DDR3 RAM with the bus speed up to 1600 MHz. The specifications of memory are DDR3 1066 MHz for one module and DDR3 1333 MHz for another. On which of the following bus speeds will the system function?
Options
- A800 MHz
- B1000 MHz
- C1066 MHz
- D1600 MHz
How the community answered
(24 responses)- A4% (1)
- B4% (1)
- C83% (20)
- D8% (2)
Why each option
When DDR3 modules of different speeds are installed together, the system operates at the speed of the slowest module. With modules rated at 1066 MHz and 1333 MHz, the system will run at 1066 MHz.
800 MHz is not the speed of either installed module and would represent an unnecessary downgrade below the slowest module's rated speed.
1000 MHz is not a standard DDR3 transfer rate and is not the speed of either installed module.
DDR3 memory controllers use the lowest common speed when modules of mixed ratings are installed, which in this case is 1066 MHz. The 1333 MHz module will downclock to match the 1066 MHz module, regardless of the motherboard's maximum supported bus speed of 1600 MHz.
1600 MHz is the motherboard's maximum supported speed but cannot be achieved because the installed modules limit the system to 1066 MHz.
Concept tested: DDR3 mixed-speed memory downclocking behavior
Source: https://www.jedec.org/standards-documents/docs/jesd79-3f
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