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12-15-2013

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t420 memory slots

2017-05-26, 21:39 PM

Awhile back I bought a us4ed T420-4177CT0 with 8G of memory, and its been a great machine. I decided to upgrade
it to 16G and bought 2 8G sticks. When I just now opened it up, there was only a single memory slot (and I looked
hard, and had a friend who has built machines look also) (see pdf). Just to make it weirder, I looked at the 8G card
in it, and it said "8G (2x4G)". So Im wondering if the solution is just to buy a single 16G card, or if there is
something someone with expertise can recommend. Thanks!

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3834 Posts

12-11-2015

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Re: t420 memory slots

2017-05-26, 22:08 PM

According to the User Manaul for you system (see Replacing memory information starting on page 123), there is a second SODIMM memory slot under the keyboard..    

 

The Detailed specifications - ThinkPad T420 document, however, states that it only supports a maximum of 8GB of RAM, but I have found that later BIOS updates often allow for more RAM that the origional Lenovo specs, and have heard that others have successfully upgraded their T420 to 16GB.

 

User Guide ThinkPad T420 and T420i

https://download.lenovo.com/pccbbs/mobiles_pdf/t420_and_t420i_ug_en.pdf

 

ThinkPad T420 and T420i Hardware Maintenance Manual

https://download.lenovo.com/ibmdl/pub/pc/pccbbs/mobiles_pdf/t420_t420i_hmm.pdf

 

Cheers,

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4345 Posts

07-24-2013

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Re: t420 memory slots

2017-05-27, 13:02 PM

As said above, the second RAM slot is under the keyboard, you need to remove two screws and lift it to see the 2nd RAM slot. Check Lenovo's HMM for more details: link (Chapter 8 - 1080)

 

16GB will work with no issues, I have three T420 maxed out like this. Just be careful when buying RAM to stay away from no-name brands and the "Value RAM" line from Kingston. Other Kingston lines like the Hyper-X should work.

 

Corsair brand is tricky with ThinkPads,  avoid the "Value Select" line at all costs. Other Corsair models branded for Apple sometimes work, sometimes not. Corsair Vengeance (their top line) works without any issues.

 

Other brands I use often are Crucial, Hynix, Elpida, Samsung, ADATA...

 

Good luck with your purchase!

 

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6 Posts

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Re: t420 memory slots

2017-05-27, 14:38 PM

Thank you so much for your reply, it is greatly appreciated. -Mark

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11-01-2018

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Re: t420 memory slots

2018-11-01, 2:27 AM

CPU-Z shows memory slots in SPD page as Slot1, Slot2. Which slot number defines as under keyboard and which under bottom?

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06-06-2011

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Re: t420 memory slots

2018-11-01, 7:54 AM
According to the HMM (linked above, chapters 1060, 1090) the sequence to install the DIMMs:
1. under keyboard
2. on the underside

I hope this matches to the CPU-Z' slots numeration.



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Re: t420 memory slots

2018-11-01, 12:50 PM
Yes, it is, this matches.
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