1.    12 Nov 2015 #1
    Join Date : Jun 2015
    Posts : 43
    (1&2) Windows 10 Pro (retail USB)

    Refused to Post after XMP Setting in BIOS


    Hi,
    Yesterday, I installed all mobo and other drivers plus various supporting software in my new build (#2 in spec with BIOS 1801). Four in the morning, all was done and I decided to end by going into BIOS to set the memory according to its 1200 MHz Factory XMP. I pressed the XMP button in the Bios and selected 2400 and then quickly "Save and Exit". In front of my tired eyes, for a short moment, I noticed "1.65 V" and something else, which seemed it should not be there. Believe XMP says 1.2 V. It did not post at all. Left it on for a few minutes, restarted a couple of times, but nothing. Turned power off on the PSU and went to bed. Today, I turned the power on, and it booted nicely all the way into Windows. Rebooted and reset BIOS to factory defaults and then changed what was necessary to get my SSD to work and PWM for the fans. Now it works nicely again.

    In the BIOS, I noticed the XMP button had not only changed the memory timings, but also fiddled with the CPU settings.

    Anyone having heard of something similar. Surely, the XMP button should only change memory timings?
    If I try to change the timings manually, I guess I do not need to change anything else? Do you think I should set the voltage to 1.2 V rather than leaving it on auto?
    What happened? Did the PSU internal protection kick in, you think?
    Last edited by Submarine; 12 Nov 2015 at 19:23.
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  2.    12 Nov 2015 #2
    Join Date : Jun 2015
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    (1&2) Windows 10 Pro (retail USB)
    Thread Starter

    Did some research and found to my surprise that, apparently, the XMP button can change quite a lot of things. Have never used one before. Guess I have to set the timings myself. (And why does the forum sporadically change initial letters in the middle of sentences to uppercase?)
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  3.    13 Nov 2015 #3
    Join Date : Oct 2013
    Texas
    Posts : 11,034
    Windows 10 Pro X64

    I would set the voltage and timings manually. Does your bios show multiple xmp choices or just to enable it?
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  4.    13 Nov 2015 #4
    Join Date : Oct 2015
    Posts : 16
    Windows 10 Pro

    I use an Asus H170 Pro Gaming mobo, which shows the XMP and Jedec settings of the RAM sticks, but there are no changed CPU settings displayed. I do think that no CPU settings should change, when the memory settings are changed. I would also guess that if you switch from Jedec to XMP, the voltage gets increased to 1.35 rather than 1.65. Have you updated the mobo BIOS to the latest version yet?

    I have seen on my system btw, that the XMP settings of my so-called PC3000-DDR4-RAM do not only increase the clockspeed and the voltage, they also use slower timing settings (17 as compared to 15, 36 as compared to 35). Looking at an excellent review of RAM speeds and their effects on the system on "Legit Reviews", I concluded that most likely, by going from 2133 to 3000, in excess of 50% (estimated) of the gain from the higher clock speed would be equilibrated by the slower timings.

    I have therefore discarded the idea of using the XMP speed. It will make them run hotter, it will wear them out faster, and it will have nearly no effect on the overall system speeds (see the above review). Apparently the CPU cache catches most RAM access, so the RAM speed is not that important anymore.

    If you want to clock them to the XMP settings, check in the BIOS what those settings are (if it shows them) and then set them manually. And if they are too far away from the Jedec settings (like 1.65 volt), then refrain from doing it. 1.65 seems very high, IMHO
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  5.    14 Nov 2015 #5
    Join Date : Jun 2015
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    (1&2) Windows 10 Pro (retail USB)
    Thread Starter

    Quote Originally Posted by Dude View Post
    I would set the voltage and timings manually. Does your bios show multiple xmp choices or just to enable it?
    There were two settings, the 2400 and one step higher.
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  6.    14 Nov 2015 #6
    Join Date : Jun 2015
    Posts : 43
    (1&2) Windows 10 Pro (retail USB)
    Thread Starter

    Quote Originally Posted by papa2jaja View Post
    I use an Asus H170 Pro Gaming mobo, which shows the XMP and Jedec settings of the RAM sticks, but there are no changed CPU settings displayed. I do think that no CPU settings should change, when the memory settings are changed. I would also guess that if you switch from Jedec to XMP, the voltage gets increased to 1.35 rather than 1.65. Have you updated the mobo BIOS to the latest version yet?

    I have seen on my system btw, that the XMP settings of my so-called PC3000-DDR4-RAM do not only increase the clockspeed and the voltage, they also use slower timing settings (17 as compared to 15, 36 as compared to 35). Looking at an excellent review of RAM speeds and their effects on the system on "Legit Reviews", I concluded that most likely, by going from 2133 to 3000, in excess of 50% (estimated) of the gain from the higher clock speed would be equilibrated by the slower timings.

    I have therefore discarded the idea of using the XMP speed. It will make them run hotter, it will wear them out faster, and it will have nearly no effect on the overall system speeds (see the above review). Apparently the CPU cache catches most RAM access, so the RAM speed is not that important anymore.

    If you want to clock them to the XMP settings, check in the BIOS what those settings are (if it shows them) and then set them manually. And if they are too far away from the Jedec settings (like 1.65 volt), then refrain from doing it. 1.65 seems very high, IMHO
    I am afraid, it did change other stuff, and this caused the computer to fail (black screen). Did not expect that, and tired as I was, I did not check before I clicked OK. Had done the same on my Z170 computer, and there only timings changed, so I did not expect any surprises. I will have to do it manually.
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  7.    14 Nov 2015 #7
    Join Date : Oct 2015
    Posts : 16
    Windows 10 Pro

    One aspect puzzles me. When I select XMP, it shows me the settings, but nothing is really changed yet. That usually, as with all settings in the BIOS, should only occur when you click on Exit and Save. You should have all the time in the world to read the settings because your BIOS should not make any changes before you click on Exit and Save .
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  8.    14 Nov 2015 #8
    Join Date : Jun 2015
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    Thread Starter

    Quote Originally Posted by papa2jaja View Post
    One aspect puzzles me. When I select XMP, it shows me the settings, but nothing is really changed yet. That usually, as with all settings in the BIOS, should only occur when you click on Exit and Save. You should have all the time in the world to read the settings because your BIOS should not make any changes before you click on Exit and Save .
    I should have yes, but it was in the middle of the night, and having done this with the other computer without problems, I just clicked exit and save and OK. Got a short glimpse of the settings changed when exiting.
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  9.    15 Nov 2015 #9
    Join Date : Oct 2015
    Posts : 16
    Windows 10 Pro

    Late night sessions are the enemy of success ;-) Good luck with changing those settings and getting the best out of your RAM!
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  10.    17 Dec 2015 #10
    Join Date : Jun 2015
    Posts : 43
    (1&2) Windows 10 Pro (retail USB)
    Thread Starter

    Did it again and now it worked just fine.
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