Wednesday, March 2, 2022

12th gen intel memory overclocking voltages

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CPU voltages

VCCIN
    Generated by the motherboard
    Used by the IVR to produces other votlages on the CPU like VCCSA and CPU VDDQ
    1.8V by spec
    Doesn't really affect anything at ambient. 

VCCSA
    Internal to the CPU and created by the IVR from VCCIN
    Powers the CPU's system agent
    Raising it can help stabilize higher IMC clocks
    I wouldn't recommend going over 1.45V for long term use.
    1.35V is usually more than enough for everything.

CPU VDDQ / VDDQTX
    Internal to the CPU and created by the IVR from VCCIN
    Powers the CPU's memory controller. Has nothing to do with the RAM sticks.
    Raising it can help stabilize higher IMC clocks
   
I wouldn't recommend going over 1.45V for long term use. (I might be overly cautious about this)
    1.35V is usually more than enough for everything.

DDR4 Specific Voltages

VDDR / memory voltage
    Generated by the motherboard
    Powers the RAM and CPU's IMC's PHYs
    Raising it can help stabilize higher memory clocks/lower memory timings
    1.2V by spec
    I wouldn't recommend going over 1.6V for long term use.
    Too much VDDR can cause stability issues by making the RAM too hot especially when above 1.45V

VTTDDR
    Generated from VDDR by the motherboard
    Used to terminate signals for the memory
    Lowering it can help stabilize overclocks on some memory ICs
    VDDR÷2 by spec

VPP

    Generated by the motherboard
    Powers the wordline of the memory chips
    Doesn't tend to affect overclocking in any way
    2.5V by spec
    Must ALWAYS be higher than VDDR

DDR5 Specific Voltages 

RAM  VDDQ
    Generated by memory stick's PMIC
    Powers the IO of the memory chips ("RAM talks to CPU using this voltage")
    Affects memory clocks and timings
    More is generally better
    1.1V by spec
    I wouldn't go over 1.6V for long term use. Should be kept within 100mv of RAM VDD
    DDR5 is temperature sensitive and runs hotter than DDR4


RAM VDD
    Generated by memory stick's PMIC
    Powers the rest of the memory chip
    Affects memory clocks and timings
    More is generally better
    1.1V by spec
    I wouldn't go over 1.6V for long term use. Should be kept within 100mv of RAM VDDQ
    DDR5 is temperature sensitive and runs hotter than DDR4

VDD2
    Generated by motherboard
    Powers the CPU's IMC's PHY when using DDR5
("CPU talks to RAM using this voltage")
    Affects memory clocks and timings
    Has motherboard specific sweet spots that can be rather low on some boards

    1.1V by spec
    I wouldn't recommend going over 1.6V for long term use.   
    On many boards less than 1.45V works best.

VPP
   
Generated by memory stick's PMIC
    Powers the wordline of the memory chips
    Doesn't tend to affect overclocking in any way
    1.8V by spec

   
Must ALWAYS be higher than VDDQ/VDD

Note:
These voltage descriptions are based on my understanding of the DDR4/5 and intel CPU documentation available to me and my expiriences with overclocking DDR4 and DDR5 on 12th gen CPUs. There might be mistakes.