Scott Mueller's Upgrading and Repairing PCs Forum

Scott,

I recently purchased a used Lenovo ThinkPad T420 in excellent condition. It has only 4 GB of RAM installed (one 4 GB module); I want to upgrade to 16 GB of memory. Yes, I know that the official Lenovo specifications state 8 GB as the maximum amount of memory this ThinkPad model supports. However, I have read multiple reports on the Internet where users have upgraded their ThinkPad T420 laptops to 16 GB of RAM and it seems to work without any problems. Also, the Kingston memory configurator actually shows an 8 GB RAM module as compatible with the T420. It also shows the maximum RAM for the T420 as 16 GB, contrary to Lenovo's specs. According to Intel, the Core i5-2520M processor installed in my T420 does support 16 GB of RAM. Perhaps Lenovo just didn't test the T420 with 16 GB of RAM before it came out, because at the time 8 GB RAM modules were so expensive that Lenovo didn't think it would be sensible to offer 16 GB of RAM as an option? What is your view on this?

The next question I have is if I can install DDR3L RAM modules in the ThinkPad T420 without having to expect any problems. The reasoning behind this is simple: As you stated in this post, DDR3L RAM is backwards compatible, but DDR3 RAM is not forward compatible. The Lenovo ThinkPad models T440 and T450 both require DDR3L RAM. Should I purchase a used ThinkPad T440 or T450 in the future, I could simply swap over the RAM modules from my T420 to one of these newer machines, but only if the RAM modules I purchase can also run at the 1600 MHz speed that these machines require.

Which leads to the next question: Lenovo's technical specs for the T420 state that this machine requires PC3-10600 Non-Parity DDR3 memory. Additionally they state, “The use of 1333 MHz SO DIMM memory is recommended for this system.” In Upgrading and Repairing PCs, 22nd Edition, you write that it is okay to use faster specification DDR DIMMs in systems that require slower ones. (Chapter 6 – Memory; page 396; last sentence in the first paragraph under the bullet points.) Have I understood that correctly, and if so, would you confirm that in this situation?

I would like to use two Crucial 8GB DDR3 PC3-12800 (DDR3-1600) memory modules (Crucial part number: CT102464BF160B) in my ThinkPad T420. Strangely enough, Crucial doesn't list that part number as compatible with either the T440 or the T450, even though Crucial's specs match the memory requirements stated in the Lenovo technical specs for these two models. It goes without saying that it is not listed as compatible with my T420 either. Crucial manufactures two different RAM modules for the T440 and T450. Part number CT4927823 for the T440 and part number CT6942318 for the T450. Why would it be necessary to offer these other part numbers for the two aforementioned ThinkPad models if they would both work properly with part number CT102464BF160B? I suspect that there are slight differences between the modules and therefore it probably isn't a good idea to use RAM modules in a system that the manufacturer doesn't recommend them for. Do you agree?

So what should I do? Is it OK for me to purchase the aforementioned Crucial RAM modules or should I stick with DDR3 (instead of DDR3L) RAM that is rated at 1333 MHz (PC3-10600) instead of the 1600 MHz (PC3-12800) required for the T430, T440, and T450?

I want to be as economical as I can from a long term viewpoint when purchasing the new RAM, however, I don't want to end up with RAM modules that don't work properly with the ThinkPad T420 I have recently purchased. Scott, what would you buy if it was your laptop?


Kind regards,

Daniel

That is exactly it. Lenovo will only advertise support for what they know is available and can be tested. At the time that model was being designed I don't think 8GB modules existed. As higher capacity modules become available it is common to find them usable in older systems. The Intel CPU and/or chipset specs normally indicate the true limits of the hardware. Note in some cases a BIOS upgrade may be necessary to have higher capacity modules be recognized.


Since DDR3L is backwards compatible that *should* work just fine, however I cannot make any guarantees.


Faster memory should almost always be able to function at any lower than rated speed. I almost always install faster rated memory than a system requires as it makes the memory more usable in other (most likely faster) systems in the future.


According to the links you posted all three modules have identical specifications. Crucial may be selling the same module under different part numbers for tracking purposes, or there may be other differences not visible in the specs (e.g. chips and boards from different suppliers). According to the specs all of them should work in your system as well as either the T440 and T450, however Crucial will only *guarantee* that they work in a system they are listed as being compatible with.


I would buy a set of one of the 3 DDR3L modules you linked to. I'm not sure it matters which one you pick since they all appear to be the same, but I'd probably pick the one marked as compatible with the system I would most likely end up moving to in the future. Scott.

now if you can add 16gb of ram to this T420 how big of a hard drive can this T420 support a 6 TB hard drive. or what?

I believe it will support a 6TB HDD, however I don't know of one that is currently available and will fit physically inside the unit. Scott.

lol Ok wiseguy. I just was being a smartbutt you know what i meant lol

ok like if you want to put in a 2tb hard drive it should work and the computer should see if full 2tb hard drive. I see that the max out hard drive is 500gb but then i would be like the ram back in the day when this computer came out the bigger hard drive cost more.

what would be a good wireless Logitech mouse for this T420. I just got the m185 model.

thanks

My previous answer is exactly what I meant to say. <g>


On a ThinkPad I only use the TrackPoint. While I haven't tested any wireless mice recently, when I have used wireless mice in the past I have had good experiences with Logitech devices. Scott.