IBM PS/2 L40 SX (8543)

[ L40 SX ]

This portable computer served me well 1996 to 2014. I bought it second-hand and only got a photocopy of the Quick Reference guide, so I decided to run the copy through a scanner and save the text and the illustrations to PDF format.

The documents are proofread a couple of times and should be an exact reproduction of the originals, but you use the information at your own risk.

Quick Reference (960KB, 120 pages)

Hints and Tips (44KB, 4 pages)

Battery Life Guide (44KB, 4 pages)

Print setup for these 3 documents: Page width = 130mm, page height = 200mm. (About 5 in. and 8 in.). Try printing 2 pages per A4 or Letter sheet in Landscape, and select "Fit to Page".

Service Manual (147KB). The L40 SX specific information, taken from the "Portable Computer Information document vol. 1" at IBM.


The rechargeable battery pack is an expensive part. It holds a total of 18 nickel-cadmium cells (2x9) that will need replacing if you buy a +10 year old computer. I have substituted the special-size cells with cheaper standard AA-size cells. It gives 45-60 minutes of portable operation, depending of the quality of the cells - not enough for serious portable use, but fine if you only want to keep the computer in a working state for fun.

NiMh batteries has a slightly different voltage than NiCad, and the L40SX computer will sound the first alert with about 15 minutes left, when using a NiMh battery pack in mint condition.

A new NiMh battery pack using cheap standard cells will last a couple of years when the computer is used on a regular basis.

When my L40 SX failed and was taken apart in 2014, it seemed to have one or more small backup batteries inside. These will also need replacement if the computer has not been used for years.

The nominal output from the AC adapter is 14,3 - 15.8 V DC, so you can make your own power supply or a car battery adapter at a low cost.

It will work with a standard 80387 co-processor from an old 386 motherboard if you find one, but the RAM is special.

Windows 3.1 knows the hardware and will modify the config.sys and system.ini files during installation as described in the Hint and Tips document. Running Windows 3.1 in "standard mode" with 2MB RAM is very slow, but old DOS software like WordPerfect 5.1, AutoCad 10 (needs the 80387 co-processor), Norton Commander 4, FastLynx, Paradox 4.5 and lots of old DOS games runs fine.

L40 SX is born with PC-DOS 5 or there about, but works with MS-DOS too.

More downloads

IBM has discontinued service for this portable computer a long time ago, and has no driver downloads, spare parts sale or service manuals on their websites.

Download rfl40103.exe (500KB) to make the Reference Diskette or download (500KB) and unzip, if your network or browser setup prevents you from downloading executable files.

The executable works in DOS, OS/2 and 32-bit Microsoft Windows, creating a bootable 1.44 floppy diskette for configuration and test of the L40SX computer. Download the Quick Reference PDF and follow the instructions for use of the Reference Diskette starting on page 43.

IBM also distributed a presentation of the L40 SX computer. It will fit on a 1.44 floppy or can be run from a command line in DOS, OS/2 and Windows (also Windows XP). Download (900KB) - unzip, run laptop.exe and enjoy the VGA graphics made by The SoftAd Group in 1991.


The harddrive in my L40 SX had difficulty spinning up for some years until it stuck. A service life of 20 years is probably more than any modern PC can manage.

My L40 SX (and an outdated Pentium 166) was disposed as toxic waste 2014-04-10. Its software was backed up and transferred to a virtual machine.

I wish you good luck if you are trying to bring an L40 SX back to life, but please notice: I can't help you with anything more than what is available on this page and its links.

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