[RavSS]

You can use the T420/T520's keyboard in a T430/T530 with modifications to the firmware, some plastic around the keyboard part itself, and the ribbon cable (just pin isolation with tape). It lets you go with Ivy Bridge over Sandy Bridge.

I have a T430 with the T420's keyboard and it lasted me 7 years of daily use before battery life became too big of an issue for me (even with a single DDR3L RAM module and a slice battery), so I put it aside. The typing experience was really excellent.

Upgrading the CPU to a quad-core model (ideally one that consumes 35W over 45W) is one of the best upgrades to make for anyone still using these machines.

[neilv]

Do you know an exceedingly credible source for the firmware modifications?

(Last time I looked, it had the air of the XDA-style culture: "To root your phone, download this package from a `.ru` piracy site, run the `.exe` on your PC, then install and run the closed blobs on your phone, including rooting and replacing your bootloader with one, we know you will trust us." Though, in their defense, if they were organized crime, they would probably make an effort to look more legitimate, rather than gratuitously suspicious. And all the forum comments were always lapping it up, appearing to be doing reckless things, while removing much of the demand and contributors for more-credible efforts.)

[RavSS]

That is the general nature of reverse engineering efforts, but this one has been documented enough that you don't need to blindly trust completely random executables or code from strange places.

You can manually recreate the process of building a patch for the embedded controller instead of just following instructions: https://github.com/hamishcoleman/thinkpad-ec. Here's the presentation by the author himself at linux.conf.au (what used to be the biggest local Linux conference for those of us in Australia and NZ): https://www.youtube.com/watch?v=Fzmm87oVQ6c. This is of course not supported by Lenovo.

Unlocking the BIOS is definitely more like what you described. It's the price to pay for freely playing around with processor power limits, getting AES-NI instruction set support, etc. I have not checked since 2019, so there might be a clearer way.

[neilv]

Excellent, thank you.

[Melatonic]

Any idea if you can get a quad core into the T420 itself ? I have a dual core i5 that is still doing decently (probably because they still sold i5 CPUs with hyper threading back then) but a quad core 35w CPU with HT would be a great pair with the dedicated Nvidia graphics.

[neilv]

Some person on Web says yes: https://forum.thinkpads.com/viewtopic.php?t=133646#p864052

There's also the W520, which looks like a T520, but is set up for a larger PSU, and had quad-core and better GPUs as factory options. (I own a few each of T520 and W520, but don't like the huge power bricks of the W. So I'm using the T as daily driver, until I really need something in the W.)