ThinkPad T420 won't see more than 4Gb of 16Gb Memory Module

[2fa]

I'm thinking this is likely to be a BIOS issue as IBM / Lenovo were (possibly still are) messing around with BIOS whitelists when the T420 was in production.

I have a 'special' BIOS installed as I used to use a 3G card with this laptop and it wasn't on the 3G card whitelist.

So I probably need to get hold of an open BIOS for this Chinese 'Intel chip' memory module.

Any old time T420 hackers around on PH these days?

Added complication is that the BIOS has a password set that I don't have so I can't get into it to alter settings, but I can FLASH a new version into the machine.

[Xenoous]

If you're able to flash a new BIOS onto the device, do that.

Quick Google come up with this if you're feeling brave? https://www.reddit.com/r/thinkpad/comments/1225zof...

[SO27]

Are you running a 32-bit operating system? Max RAM size for that is 4GB.

[Xenoous]

SO27 said:

Are you running a 32-bit operating system? Max RAM size for that is 4GB.

Was my first thought too, but OP seems to know his onions so figured I'd not insult them by saying so

[maffski]

A single module? I don't think the T420 supports more than 8Gb modules.

[2fa]

I don't know nuffink.

64 bit Win10 OS.

I'd forgotten that I'd done the bios chip reset thing a few years ago so I can get into the bios but there's nothing in there to change for memory size allocation.

There's an advanced section in the bios that's password protected and I don't know the default password.

I may take another look and post up details later.

Yes it's a single slot but the board can take a single 16Gb stick according to many posts around the internet.

Guess I may need to buy a proper hardware memory module for more bucks to get it to work.

Interesting that the 1st 4GB can be seen and accessed without any memory problems.

Remember having similar issues years ago with my much loved 486 board and cheap memory modules.

Think a 1Mb stick cost around £40 or more in those days iirc!.

[maffski]

2fa said:

...Yes it's a single slot but the board can take a single 16Gb stick according to many posts around the internet...

My internet seems to suggest it's dual slot (2x8GB), although weirdly with one slot on the bottom and one slot under the keyboard - never seen that before

https://www.youtube.com/watch?v=W80l5LeA4OA&ab...

[Jinx]

maffski said:

My internet seems to suggest it's dual slot (2x8GB), although weirdly with one slot on the bottom and one slot under the keyboard - never seen that before

https://www.youtube.com/watch?v=W80l5LeA4OA&ab...

I'm thinking the OP's laptop is only seeing the 4GB SoDIMM under the keyboard and the 16GB in the accessible slot is not registering at all.

[2fa]

Jinx said:

I'm thinking the OP's laptop is only seeing the 4GB SoDIMM under the keyboard and the 16GB in the accessible slot is not registering at all.

Yes correct.

I'd unknown knowned the under keyboard memory slot that I'd put a 4Gb stick in 6 years ago.

I'd so forgotten about it that I was surprised when I found it (thanks to poster above with YT link).

Anyway now have 2x 8Gb sticks working fine.

I'll keep the 16Gb stick and try to put it in the single slot in 6 years' time.

Or possibly next week

[colin79666]

We had T420s at work years ago. Great laptops, the last with the proper keyboard!

Think these were 2nd gen core i5/7 machines, so 8GB is the max module size. You can run them 2x8GB with certain modules but not 1x16GB.