12th Generation Intel® Core™ Processors Datasheet, Volume 1 of 2


ID 655258
Date 28/10/2021 00:00:00
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Document Table of Contents

Disabling Unused System Memory Outputs

Any system memory (SM) interface signal that goes to a memory in which it is not connected to any actual memory devices (such as SODIMM connector is unpopulated, or is single-sided) is tri-stated. The benefits of disabling unused SM signals are:

  • Reduced power consumption.
  • Reduced possible overshoot/undershoot signal quality issues seen by the processor I/O buffer receivers caused by reflections from potentially unterminated transmission lines.

When a given rank is not populated, the corresponding control signals (CLK_​P/CLK_​N/CKE/ODT/CS) are not driven.

At reset, all rows should be assumed to be populated, until it can be proven that they are not populated. This is due to the fact that when CKE is tri-stated with a DRAMs present, the DRAMs are not ensured to maintain data integrity. CKE tri-state should be enabled by BIOS where appropriate, since at reset all rows should be assumed to be populated.