T420 Memory Slots

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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.

Again, brand does not matter.At all. The only thing that different brands of RAM offer are different labels. Ostensibly some brands have different QC than others, but that doesn't really matter; this isn't like hard drives where QC affects the lifespan of the product - either the RAM works and passes memtest, in which case you keep it, or it doesn't, in which case you. Well, I'm ordering the T420 with stock RAM and upgrading myself. Problem is I don't know which type to get? There's different speeds and different pins like 200-pin. I just don't know which type of RAM is compatible with the T420. Anyone can shed some light on this is greatly appreciated!

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

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.

Thinkpad t420 memory

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.


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.

I may never buy a new laptop computer again.

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Save up to 38% on new PowerEdge server configurations here.

Help deliver robust performance, scalability and reliability to your organization with the ample power, memory and I/O bandwidth of the PowerEdge™ T420 tower.

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PowerEdge T420 Tower ServerPowerEdge
  • Intel® Xeon® processor E5-2400 and E5-2400 v2 product families
    Processor Sockets:
    Internal Interconnect:
    Intel QuickPath Interconnect (QPI) link: 6.4GT/s; 7.2GT/s; 8.0 GT/s
    2.5MB per core; core options: 4, 6, 8, 10
  • Microsoft® Windows Server® 2012
    Microsoft Windows Server 2008 R2 SP1, x64 (includes Hyper-V®)
    Novell® SUSE® Linux Enterprise Server
    Red Hat® Enterprise Linux®
    Virtualization options:
    Citrix® XenServer®
    VMware® vSphere® ESXi ™
    Red Hat Enterprise Virtualization®
  • Up to 384GB (12 DIMM slots) 2GB/4GB/8GB/16GB/32GB DDR3 up to 1600MT/s
  • Choose from four 3.5” cabled, eight 3.5” hot-plug, or sixteen 2.5” hot-plug drive bays
  • Form factor:
    Tower (5U rackable)
    Rack Support:
    ReadyRails II sliding rails for tool-less mounting in 4-post racks with square or unthreaded round holes or tooled mounting in 4-post threaded hole racks, with support for optional tool-less cable management arm (for rackable chassis model only)
  • Optional high-efficiency, hot-plug, redundant power supplies; hot-plug drive bays; TPM; dual internal SD support; redundant fans; optional bezel; luggage tag; ECC memory; optional interactive LCD screen; extended thermal support; ENERGY STAR® compliant; switch independent partitioning
  • Power Supply:
    Titanium efficiency, hot-plug, redundant 750W power supply
    Platinum efficiency, hot-plug redundant 750W or 1100W power supplies
    Auto-ranging power supplies
  • Internal controllers:
    PERC S110 (SW RAID)
    PERC H310
    PERC H710
    PERC H710P
    External HBAs (RAID):
    PERC H810
    External HBAs (non-RAID):
    6Gbps SAS HBA
  • Intel C602
  • Maximum Internal Storage:
    Up to 32TB

    Hard Drives:

    Hot-plug hard drive options:
    2.5” SATA, nearline SAS, SAS (15K, 10K), SAS SSD, SATA SSD, SAS 512n (15K)
    3.5” SATA, nearline SAS, SAS (15K)
    Self-encrypting drives available

    Cabled hard drive options:
    3.5” SATA, nearline SAS, SAS (15K)
  • 6 PCIe slots:
    Two x16 slot s with x16 bandwidth, 3.0, full-length, full-height
    One x8 slot with x4 bandwidth, 3.0, half-length, full-height
    One x8 slot with x4 bandwidth, 2.0, half-length, full-height
    One x8 slot with x4 bandwidth, 3.0, full-length, full-height
    One x8 slot with x1 bandwidth, 2.0, full-length, full-height

  • Embedded NIC:
    Broadcom® 5720 GbE Dual Port 1Gb LOM

    I/O adapter options:

    1Gb Ethernet:
    Broadcom 5720 Dual Port 1Gb NIC
    Broadcom 5719 Quad Port 1Gb NIC
    Intel I350 Dual Port 1Gb stand-up adapter
    Intel I350 Quad Port 1Gb stand-up adapter
    10Gb Converged Ethernet:
    Brocade® BR1020 Dual Port 10Gb CNA
    Qlogic® QLE8262 Dual Port 10Gb DA/SFP+
    Broadcom 57810S Dual Port 10Gb Base-T CNA
    Broadcom 57810S Dual Port 10Gb DA/SFP+ CNA
    10Gb Ethernet:
    Intel X520 Dual Port 10Gb DA/SFP+ server adapter
    Intel X540 Dual Port 10Gb Base-T adapter
    FC8/FC4 HBA:
    QLogic QLE2460 4Gb Single Port FC HBA
    QLogic QLE2462 4Gb Dual Port FC HBA
    QLogic QLE2560 8Gb Single Port FC HBA
    OLogic QLE2562 8Gb Dual Port FC HBA
    Emulex® LPe-12000-E 8Gb Single Port FC HBA
    Emulex LPe-12002-E 8Gb Dual Port FC HBA
    Brocade 815 8Gb Single Port FC HBA
    Brocade 825 8Gb Dual Port FC HBA
  • Remote Management:
    Basic management (default)
    iDRAC7 with Lifecycle Controller
    iDRAC7 Express (upgrade option) or iDRAC7 Enterprise (upgrade option)
    8GB or 16GB vFlash media (upgrade options)
    Systems Management:
    IPMI 2.0 compliant
    OpenManage™ Essentials
    OpenManage Power Center
    Dell OpenManage Connections:
    • OpenManage Integration Suite for Microsoft® System Center
    • Dell plug-in for VMware® vCenter®
    • HP Operations Manager, IBM Tivoli® Netcool®, and CA Network and Systems Management (NSM)
  • Rack Support:
    ReadyRails™ sliding rails with optional cable management arm for 4-post racks (optional adapter brackets required for threaded hole racks; for rackable chassis model only)
  • Product Safety, EMC and Environmental Datasheets
    Dell Regulatory Compliance Home Page
    Dell and the EnvironmentENERGY STAR®
    The Dell PowerEdge T420 has earned the ENERGY STAR® Enterprise Server designation.
    ENERGY STAR and the ENERGY STAR mark are registered U.S. marks, Click here (In English).

Balanced processing, memory and I/O

Start building your future with PowerEdge T420, a workhorse tower server engineered to deliver performance, expandability and reliability in a quiet office setting.
Productive performance
Help enhance office productivity with the two-socket PowerEdge™ T420, powered by the Intel® Xeon® processor E5-2400 and E5-2400 v2 product families. Matching the fast and efficient processing with a dense memory footprint enables small and midsize business offices to crunch through critical business applications quickly and efficiently.
Advanced I/O
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Outstanding efficiency and availability
Help keep your workplace efficient, your operating expenses in check and your workflow secure with the T420’s designed-in reliability, availability and serviceability features.
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Dell™ Services can help reduce IT complexity, lower costs and eliminate inefficiencies by making IT and business solutions work harder for you. The Dell™ Services team takes a holistic view of your needs and designs solutions for your environment and business objectives while using established delivery methods, local talent and in-depth domain knowledge to help you lower your total cost of ownership.
Dell offers a wide range of professional services to simplify the assessment, design, implementation, management and maintenance of your IT environment and to help you transition from platform to platform.
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Dell ProSupport offers a suite of support services that enable you to choose support models based on how you use technology and where you want to allocate resources. We recommend Dell ProSupport Plus withSupportAssist for mission-critical systems or Dell ProSupport for premium hardware and software support for your PowerEdge solution. For hyper-scale data centers, we also offer ProSupport Flex for Data Center. Contact your Dell representative today for more information*.
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Dell OpenManage Systems Management portfolio
The Dell OpenManage systems management portfolio, including Dell PowerEdge server embedded management feature integrated Dell Remote Access Controller (iDRAC) with Lifecycle Controller, helps IT Administrators efficiently manage Dell servers in physical, virtual, local and remote environments, operating in band or out of band, with or without a systems management software agent. Irrespective of the operating system or hypervisor you deploy, iDRAC with Lifecycle Controller automates the most essential and frequently performed server management tasks to help your IT resources become more productive and your IT environment more cost-effective and well-maintained. Dell OpenManage also integrates and connects to leading third-party systems management solutions you may already own, so you can maintain your single point of control and capitalize on your existing investment.
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Dell Desktop Virtualization Solutions
You face an expanding set of challenges for provisioning, managing and supporting end-user computing across your enterprise. Your IT team is not growing, but support requirements are more complex as you plan how best to migrate and update client systems, and secure new “smart” mobile devices.
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Lenovo T420 Memory Slots

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Lenovo T420 Max Ram

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Dell’s open, standards-based solutions let customers of all sizes integrate new technologies without sacrificing performance or their existing IT investments.
Direct-Attached Storage:
The Dell PowerVault MD storage family offers easy and economical expansion for Dell PowerEdge servers enabling high availability and scalability for demanding business applications.
Disk-to-Disk Backup
Due to expanding volumes of data that must be backed up and protected along with shrinking backup windows, many IT departments have moved to or added disk-based backups.
Network-Attached Storage
NAS is a specialized storage server with its own IP address that is made available to multiple clients and servers on a local area network (LAN) or wide area network (WAN).
Object-Based Storage
The Dell DX Object Storage Platform is designed to intelligently access, store, protect and distribute fixed digital content.
Storage Area Network
A storage area network (SAN) is a network of shared storage devices, such as disk storage arrays and tape automation
Tape Backup
Considered the first and last line of defense against data loss, tape and removable disks can be used for long-term data storage and backup.
Unified Storage
Unified Storage is a term that describes the ability to manage both file- and block-level data.