The t420 comes with 4G installed. I know how to add another 4G to it though the slot at the back. But I'd add as much memory as possible. So I have two questions
1. Is it possible to add a secondary 8GB at the back slot? the 8G and the existing 4G won't match in size so I am not sure. Has anyone done that?
2. where is the other memory slot and how to access it in case I need to match the chips up to 2x8GB.

Thanks!

The secondary memory slot can be accessed from the underside of the notebook, from the door provided for the purpose. The first memory module is housed under the Keyboard, and can be easily accessed. i suggest a look at the Workshop manual and a few youtube videos to see how it can be done. Easy as Pie.

I would stick to a 4X2 or 8X2 configuration, rather than have mismatched memory sizes, simply for reasons of letting both memory channels work with equal amounts of RAM. if you look elsewhere in this forum, people have successfully integrated 16 gigabytes into their T420 machines. question is the high cost of 8gb modules and the benefit a user can derive from them.

There is no problem in using 2 different manufacturer's RAM modules, as long as the Specs are the same. I use a cheap PNY 4gb module i picked up from the local BestBuy and it works perfectly. There's nothing remotely exotic about the RAM required by the Thinkpad, so it is widely available.

Yep can definitely use 16gb in a T420 (see my signature below). I purchased my ram in beginning of March for $119.99 from Newegg.com, it's this RAM: http://www.newegg.com/Product/Product.aspx?Item=N82E16820233217 currently on sale for $109.99 with free shipping.

Hi,

I know this is an old track but I can’t help but need to confirm the RAM module before I make the investment on it.

I just acquired my Lenovo T420 2 weeks ago. (System Model:- 4236QS0. i7-2640m, BIOS Version/Date LENOVO 83ET67WW (1.37 ), 2011-11-28)

At present, there is only 1 piece of 4GB RAM in the system and I intend to upgrade it to the maximum – 16GB RAM.

I will be running a number of virtual systems in this baby thus I do need all the memory I could grab.

I checked out on the Kingston’s website by looking at the compatibility list. T420 does shows up with the 8GB RAM as an option. The entire listings for it will be 2GB, 4GB and 8GB. However, 8GB RAM seem to be not available, yet.

From the forum, through those who successfully installed and running the 16GB memory, it shows most of them are running on Corsair.

I search on the web and found the following kit;

16GB DDR3 1333MHz RAM (2x 8GB Corsair CMSO8GX3M1A1333C9)

Is this the correct RAM module to use it on the Lenovo ThinkPad T420?

Or should I get the “ Corsair Vengeance” instead?

Thank you very much for kind assistant in advanced.

Regards

a pair of 1333mhz DDR3 SO-DIMM 204 pin 8gb sticks are all you need. you dont HAVE to buy a matched pair, but it helps (maybe you get better pricing on pairs)

1600mhz RAM is not worth the expense, as i don't think you want to overclock your notebook...nor is ECC RAM.

go ahead and get the RAM that matches the above specs.

I am using 8gb of ram on my t410 machine, When I have choosing the ram I have looked on specification and there was info about 16 gb only at ddr4 sticks, is it possible to find ddr4 sticks now ?

Maybe anyone has the 16gb on ddr3 in t410?

regards

I just wish to update my last post pertaining to the 16GB and T420.

I have successfully installed and operating the 16GB memory that I acquired from Amazon last week.

Ran the memory advanced integrity test for 20 pass and Passed!

I could really see the performance gained! Especially when launching the IE browser.

Now, my next target will be getting a mSATA as my boot drive!

Unfortunately, 8gb of RAM is the maximum for your T410. I previously had a T410 and I tried to upgrade the RAM past that and the machine would POST, but not boot an OS - it couldn't address all of the memory. Sorry, but if you have 8gb of RAM you are already maxed out on the T410. It's why I sold mine and bought a T420 actually.

I ordered this 16GB kit today for $91.xx (w/free shipping) from Newegg

Cool. It's really coming down in price, a friend ordered a set for $79.99 on a weekend special. They are working great for me, hope the same for you.

Yeah, it's silly when you consider how much 2GB cost a few years ago.

Did you have to alter anything in the BIOS or make any other changes, Wolfman?

Thx.

The only changes I made in the BIOS were to boot in legacy BIOS mode instead of UEFI or the hybrid mode (can't remember what they call it, but it was the default option). Other than that, no additional changes were required in the BIOS. I booted it, burned the recovery disks, took out the hard drive, put in the SSD, installed linux, added the ultrabay HDD adapter, formatted the 750gb drive and started moving over VM's.

Got it, thanks! I've just got the standard 7200rpm h-drive, so it's simple for me.

Hello everyone ,

I have 1 x 4 GB memory installed and i was wondering if by using 2 x 4 GB will speed up my machine when ram usage is below 4 GB on a win7 system.

If i upgrade to 1x4 gb and 1x2gb with the same clock specs will the difference in size play any part in the performance?

Thanks

It simply depends on what you are doing with the laptop. The memory is in a dual channel arrangement, so by having both slots populated, these is a performance increase during certain tasks. However, there are not many tasks where the memory is the bottleneck. It will benchmark better, but it is unlikely that you will notice an increase in speed.

I think I notice a slight improvement in overall performance. There is a clear improvement when doing intensive stuff with foto processing, etc.

My boot up times are horrid on this T420 (WIN7). I've done multiple measurements and my time is about 2 mins 40 seconds to get to the log-in window and then another 60 - 70 seconds to the desktop. I will say that shutdown times are outstanding - - probably better than any other machine I've worked on. The start up times are the worst, but I've got to deal with all sorts of stuff running that can't be skipped I played around with the Lenovo "RapidBoot Shield" program and that's bordering on worthless. In fact, I think it slowed the boot-up time. Not sure how many complete re-starts it needs to work its magic, but I've left it in place for 2 weeks and lots of re-starts and there really wasn't much improvement, if any at all

I've had problems with this Corsair memory over the past week. I had a serious BSoD event and the computer would no longer boot. During my diagnostic tests one of the memory sticks came back as FAILED. It doesn't give me any other info beyond that.

I'm RMAing both sticks back to Corsair.

Unfortunately I see others are having similar issues when you go out and read contemporary Newegg reviews of this product

That's unfortunate. I've had very good luck with corsair desktop memory, I've never tried their laptop memory.

Hopefully this will not jinx me, but I've had good luck with the 2x8gb Corsair sticks in my T420 for the past year. I'm sure they will get you a replacement stick and you'll be all set minus the inconvenience.

Thanks. I've already ordered Crucial memory to replace the Corsair. I'll just eBay the Corsair when I get them back from the mfr to offset the expense.

Good luck with the Crucial. I'd run memory tests on it overnight. There are bad sticks from all the major brands from time to time.

Will do. How many hours do you think it will take?

Thx.

Last time I did it, I ran them for 10 hours. I usually try and do 12. Some people swear by 24 hours, but I've never done that personally. The minimum I've done for one of my own machines is 4 hours. Hope that helps.

Very good. Thanks again.

(I'll have to read up on it...it's been a long time since I've run it.)

For memtest86 I usually let it go 3 passes. That can take awhile depending upon how much memory you have.
That being said, when I have bad ram it has always failed first pass.

Thanks, Funky. I've only got 1 strip of 8GB in the machine. The bad strip has been removed. I let it run for about 10hrs last night..It was still grinding away this morning but with 0 errors.