I recently purchased a used Lenovo Thinkpad T420 laptop to replace the Lenovo Thinkpad T400 I was previously using as my main platform for researching open-source network simulators and emulators. The T420 is a five-year old product but it offers all the ports and performance I need. Because it is well past its depreciation curve, anyone can purchase a used T420 for a very low price.

I wanted a computer that supports high-resolution external monitors so it required a DisplayPort output. I also wanted to expand the number of VMs I can run concurrently with adequate performance so I needed a processor that supports HyperThreading. I wanted to switch to the Ubuntu Linux distribution and the Ubuntu Unity desktop environment needs just a bit more processing power to run smoothly. The Lenovo Thinkpad T420 meets all these requirements.

Continue reading to learn more about the Lenovo Thinkpad T420, another excellent and inexpensive Linux platform.

The Lenovo Thinkpad T420

With its 2.5-GHz Core i5 CPU, 4GB of RAM, an Nvidia NVS 4200M graphics chip, and 7,200-rpm hard drive, the ThinkPad T420 was strong enough for anything we threw at it, from playing 1080p video to.

• 2019 UPDATE: Recommended 2.5' SATA III SSD: are the upgrades I made to my Lenovo Thinkpad T420. I'm sure this voids the warranty.
• Lenovo ThinkPad T420 Upgrade Project. The two sticks of RAM I took off from the T420. Since I did not intend to use a SIM card on this T420, I can re-purpose this slot to an M-SATA.
• 2019 UPDATE: Recommended 2.5' SATA III SSD: are the upgrades I made to my Lenovo Thinkpad T420. I'm sure this voids the warranty.

The Lenovo Thinkpad T420 is a business-class notebook produced in 2011 that was leased in large volumes by companies for use by their employees. Now, these companies are returning these computers to the leasors so Lenovo T420 laptops are available at used-computer re-sellers and on eBay at very low prices.

When purchasing a used Lenovo T420, you need to be aware of what you will get for your money. The Lenovo Thinkpad T420 was originally produced in many different configurations. When comparing prices, take into account the features added to the computer.

When looking for a used T420, I suggest you purchase a model with the 1600×900 LED screen. Other parts of the T420, such as the hard drive and memory, are easy to upgrade. Some models of T420 come with a discreet NVIDIA graphics chip, which is not important for most users so don’t pay extra for it. Some models offer a fingerprint reader, which is a convenience.

Upgrading memory on a Thinkpad 420 is very easy. When Lenovo installs the base level of memory in a Thinkpad, it only uses one memory slot so it is inexpensive to upgrade the laptop to 8GB by purchasing one more 4GB DIMM — and the second slot is very easy to access.

Replacement parts for the T420 are still available and Thinkpads are made to be easily repairable. You can download the T420 maintenance manual from the Lenovo web site. For example, the T420 I purchased has a few keys on which the letters are fading. If I decide to replace these keys, I can find multiple online stores that sell replacement keys just by searching for “thinkpad T420 key replacement” on Google.

My T420

The T420 I purchased was a well-equipped model with the Intel i5-2540M processor, a 1600×900 HD+ LED screen, Intel HD Graphics 3000 and NVIDIA NVS 4200M discreet graphics with Optimus graphics switching technology, a fingerprint reader, a webcam, 4GB memory, and a 320 GB 5400 RPM hard drive. It also has four USB2 ports, a Firewire port, a VGA output, and a DisplayPort output that supports an external monitor with up to 2560×1600 resolution. It came with Windows 7 Professional already installed.

All this cost me just $280 in Canada (or US$200), so it was very inexpensive for a well-built computer that will last me two to three years.

Install Linux on a Thinkpad T420

I describe the Linux install process and the software I use on my computer setup page.

Ubuntu Linux works very well on Thinkpads so the installation should be painless and Ubuntu should automatically set up a dual-boot system if Windows is already installed on the laptop.

NVIDIA graphics in Linux on Thinkpad T420

As mentioned above, the T420 I purchased has an NVIDIA NVS 4200M discreet graphics chip. In Windows, the laptop will switch between the Intel graphics and the NVIDIA graphics as required by programs running. Unfortunately, the graphics switching technology does not work well in Linux so we must do some extra configuration to enable manual graphics switching, or just disable the NVIDIA graphics in the BIOS settings.

By default, Ubuntu Linux uses the NVIDIA graphics chip if it is installed. This offers high performance but it uses up battery power a lot faster than the Intel graphics. To improve battery life, you may install the NVIDIA driver that will allow you to manually enable and disable the NVIDIA graphics chip so you can choose between performance and battery life.

NVIDIA Graphics and Windows

The T420 I purchased came with Windows 7. When I booted up Windows 7, it offered a free upgrade to Windows 10. I chose not to upgrade to Windows 10 because it is not clear if the NVIDIA Optimus graphics switching technology will be supported in Windows 10.

Lenovo does not officially support the T420 with Windows 10 so they will not provide updated Windows 10 drivers. Without the right drivers for the NVIDIA chip and for power management, battery life may be much shorter in Windows 10.

For now, I will keep Windows 7 so that the NVIDIA switchable graphics and Lenovo power management features continue to provide good battery life when I run Windows.

Conclusion

Lenovo T420 Thinkpad Specs

In the past five years, computer performance has been “good enough” for most activities. Open-source software, such as Linux, runs very well on older computer hardware and provides all the newest features and security updates. Today, most people may be well served by a computer that is four or five years old. These older, used computers are very inexpensive to purchase.

I am very pleased with the performance of my used Thinkpad T420 laptop when running Ubuntu Linux. In two or three years, I will upgrade to a Lenovo T450 or X1 Carbon when those models are close to the same US$200 price point that the T420 is at today.

Lenovo Thinkpad T420s

I may never buy a new laptop computer again.