T420 ThinkPad RAM upgrade compatibility question?

[Liam Proven]

On Tue, 15 Oct 2024 at 15:12, Ian Bruntlett <ian.bruntlett at gmail.com> wrote:

>
> Ah. OK. I have two T420 ThinkPads.

OK, so both Core i5 models.

There are 6 different speed grades of DDR3 memory:

DDR3-800 (PC3-6400)
DDR3-1066 (PC3-8500)
DDR3-1333 (PC3-10600)
DDR3-1600 (PC3-12800)
DDR3-1866 (PC3-14900)
DDR3-2133 (PC3-17000)

The faster, the more expensive, but there is not a lot in it.

I bought my RAM from CEX, because it's much much cheaper used. 8GB
SODIMMs are only about a fiver now.

https://uk.webuy.com/

But unless you are local enough to visit a shop, you have to mail
order. My local branch is a small one and didn't have much DDR3 in
stock. i ordered online and sadly got mismatched modules.

You absolutely want matched pairs.  Mismatched may work but it can be
unreliable and that's no use.

So, now, my i7 T420 has 16GB, but the quad-core i7 W520 I am typing on
has only 24GB because one module doesn't play nice. it has 2 8GB and 2
4GB modules. I have two 8GB ones sitting in a bag that I can't use,
and a matched pair of 4 GB modules seemed preferable.

(I have an i5 T420 with screen issues that dual-boots FreeBSD and
ChromeOS Flex, and I plan to try the leftovers in that.)

Reddit tells me that you can go at least 1 speed grade higher.

https://www.reddit.com/r/thinkpad/comments/rxe1dc/can_anyone_recommend_me_2x8_gb_ram_sticks_to/

So I would recommend getting at least PC3-12800 and preferably
PC3-14900 modules. The machines will use them. With the integral Intel
GPU you may get more benefit.



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