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Paper Tape
Posts: 2
Registered: ‎08-11-2017
Location: CA
Views: 7,337
Message 1 of 8

ThinkPad P51 RAM question regarding RAM slots

The P51 can hold 64gb ram divided in two seperate locations.  One of which is easily accessable, the other which is a little more difficult.

My question is if I order 8gb ram and manually upgrade the ram myself to 16, which slot does the manufacture place the 8gb memory stick in ? The easily accessable slot or the more difficult slot?


Because if the manufacturer leaves the easy accessable slot empty I will be more likely to make a purchase to upgrade myself and save money in the process.

Token Ring
Posts: 254
Registered: ‎12-08-2008
Location: US
Views: 7,303
Message 2 of 8

Re: ThinkPad P51 RAM question regarding RAM slots

to be honest, my first reaction would be just to open the bottom panel, there a just a few screws and you will know for sure. there must be a way to tell from the BIOS or CPU-Z to know which dimm slots are used, and then use the service manual to know which slot is which, but just opening up the bottom panel shoudl be a 3 minutes thing and you can see if the two slots there are empty).
Paper Tape
Posts: 2
Registered: ‎08-11-2017
Location: CA
Views: 7,298
Message 3 of 8

Re: ThinkPad P51 RAM question regarding RAM slots

Yes.  However, I would like to know before making the purchase.  Because in this video you can see that the first ram slots are easily accessable whereas the second ram slots are no where near as easily accessable.  I would just like to know in advance.  Thanks though for your response.

Posts: 2,319
Registered: ‎06-13-2013
Location: US
Views: 7,305
Message 4 of 8

Re: ThinkPad P51 RAM question regarding RAM slots

Please read this other thread entitled "Do I need to install RAM in pairs" to get answers about populating the four memory slots, performance comparison from "single channel mode" vs. "dual channel mode" (reputed to be 10-15% faster than "single channel mode"), etc.


The two harder to access under-the-keyboard slots (#3 is the upper and #1 is the lower, with #3 lying over #1) are where Lenovo installs all 1x or 2x memory configurations that you purchase.  If you buy a 1x setup (either 1x8GB or 1x16GB) that stick will be in the #3 slot.  If you want to add your own second matching (size and speed) memory stick you should do it in the other "paired" slot of this pair, namely in #1, if you want to have optimal "dual channel mode" performance.  That means you have to get to this location under the keyboard, which you already know is more difficult.


Lenovo 1x8GB=8GB and 1x16GB=16GB configurations involve only one memory stick, delivered under the keyboard in #3.  You have to go up to at least 32GB from Lenovo (2x16GB=32GB) in order to have the factory populate both #3 and #1 under the keyboard for you.  If you go up to 64GB (4x16GB=64GB) all four memory sockets will arrive populated.  Anything else is do-it-yourself, and you now have the information you requested about sockets and their usage.


If you just go ahead and order some more expensive 2x memory configuration from Lenovo (i.e. 2x16GB=32GB or 4x16GB=64GB) then Lenovo will at the very least put those two memory sticks in this under-the-keyboard location (#3 and #1) or will populate all four slots (i.e. #3 and #1 under-the-keyboard as well as the two easy-to-access #4 and #2 sockets directly accessible on the underside of the laptop).  Note that #2 and #4 are not only easy to get to simply by removing the cover on the underside of the laptop, but they're both "flat, side-by-side" so you can easily insert two memory sticks into these two sockets.


Dual-channel mode performance requires a matched pair of memory sticks in either or both of the "pairs" (i.e. using just #3/#1, or just #4/#2, or all four slots #3/#1 and #4/#2).  You can have two different sized memory sticks in each "pair" (e.g. one pair can be 2x8GB and the other pair can be 2x16GB, but each pair should have two identical cards), but each pair of sticks must be the same size and all of the memory sticks must have the same speed (else the BIOS will simply run the faster memory at the lesser slower speed of the slowest memory).  Any other odd configuration (e.g. 1 or 3 sticks of memory, mismatched memory stick sizes or speeds, etc.) will result in the slower single-channel performance.

Blue Screen Again
Posts: 1
Registered: ‎05-21-2018
Location: US
Views: 4,586
Message 5 of 8

Re: ThinkPad P51 RAM question regarding RAM slots

I have read this response and have followed a similar process on Youtube to install a second 16MB RAM into slot #1 (originally had just 1 16MB in slot #3).  I then reassembled the computer and rebooted.  The computer is not recognizing the new 16MB stick.  When I check the system it shows only 1 slot being used.  I am certain I had the new stick click into the port.


I have had people tell me that I need to go into the BIOS, disengage the internal battery and then re-engage it.  I am not seeing this option in the BIOS and did not find online the need to do this as well. 


Does this step seem correct or does it seem as though I may have missed a step elsewhere?


Thank you.

Community SeniorMod
Community SeniorMod
Posts: 10,007
Registered: ‎01-01-2010
Location: US
Views: 4,583
Message 6 of 8

Re: ThinkPad P51 RAM question regarding RAM slots

You shouldn't need to do anything to recognize more RAM.  It is either a bad slot, an incompatible stick ir incorrectly inserted.  If you cannot fix it from this, start a new thread.


I do not respond to requests for private, one-on-one help. Your questions should be posted in the appropriate forum where they may help others as well.

If a response answers your question, please mark it as the accepted solution.

I am not an employee or agent of Lenovo.
Posts: 108
Registered: ‎09-05-2016
Location: US
Views: 4,514
Message 7 of 8

Re: ThinkPad P51 RAM question regarding RAM slots

I just installed 2x8 GB of RAM in slots #2 and #4.


They were immediately recognized by the system after reboot:


RAM Upgrade.JPG

- All RAM (4 x 8 GB) is working in dual channel.


- No BIOS changes needed.



P50 - Xeon E3-1535M v5 - 32 GB RAM - FHD display - Quadro M2000M - Win7 x64
Vacuum Tubes
Posts: 26
Registered: ‎08-31-2015
Location: DO
Views: 2,882
Message 8 of 8

Re: ThinkPad P51 RAM question regarding RAM slots

Hi everyone

Any opinion for my situation?



Arturo Polanco

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