A question ASUS first level could not answer me about ddr4 "Auto" setting.
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  1. #1
    Join Date
    Jun 2005
    Montreal, Que, Canada
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    A question ASUS first level could not answer me about ddr4 "Auto" setting.

    My question to ASUS was about ddr memory tweaking. I got the user manual explanation and nothing more.

    My ASUS bios shows me my ddr4 ram speed as "Auto". What does Auto mean? I bought ddr4 3000 speed with 15,15,15,35 timing. (I presume that the numbers are clock ticks and that ram will run at 1500mhz minus (1500 *70 nanoseconds) or about 1475mhz.
    My bios indicates 2350 as the DDR4's Jedec value so ddr4 speed is based on the jedec value. so, if DDR4 is double rate, can my DDR4 memory deliver results at 4700mhz/sec?

    When I deselect auto, the bios shows the ddr4 speed set to 2950 (2x1475). Does it mean, the ram is pegged at that speed irrespective of cpu load? Am I right to assume that based on design values, the cpu speed does vary with load, and ddr4 auto also means that that the ddr4 ram will track cpu speed?. If I peg my ddr4 ram to 3200, is that ddr4 speed fixed?

    The bios program is from "American Megatrends". The user manual is not meant for other than plug and pray. I always thought that the bios was there to start the system and provide an interface between Linux and the hardware. Thereafter, it is out of the picture until the next system boot.

    So what is "auto" wrt ddr4?
    Leslie in Montreal

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  2. #2
    Join Date
    Dec 2013
    United Kingdom
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    Re: A question ASUS first level could not answer me about ddr4 "Auto" setting.

    ASUS first level support...next time ask Alice

    Auto uses the Serial Presence Detect values from the installed RAM chips. The JEDEC value of 2350 is already multiplied.

    For your Ryzen forget 3000MHz, you should use manual timings of 2933-15-15-15-35, also don't use 3200 if your RAM is rated for 3000 as it will cause instability issues and knacker it far quicker:


    DDR speeds are indeed fixed, the power saving clock variance only applies to the CPU cores and not the RAM.

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