The L40SX is a well-built IBM laptop that was part of the PS/2 (Personal System/2) lineup, released around 1991. It has a 20MHz 386SX processor, with a hardware switch to adjust the speed between Automatic and User-Defined.

It has a monochrome sidelit screen (since this was before the CL57SX), but it’s surprisingly crisp and clear. The keyboard is the best laptop keyboard I have ever felt; they tried to imitate the IBM Model M Keyboards of the time! In fact, IBM sold a version of this laptop’s keyboard with a built-in TrackPoint, the IBM Model M4-1.

My first L40SX came with 4 MB of RAM; my second came with 6 MB. Over the years, I’ve replaced the CMOS battery, hard drive (standard IDE with a Dynamic Drive Overlay seems to work fine) and batteries. These are neat machines, but be aware that if the CMOS configuration is lost, you will need to boot from a floppy to reconfigure the machine (as was common on PS/2 machines of the time). Without this, the laptop will not be able to see the hard drive configuration, and will boot to a built-in ROM version of the BASIC programming language.

Trackpoint

The L40SX had an optional “Trackpoint” pointing device, but it’s not the one you would find built into a ThinkPad! In this case, “Trackpoint” refers to an external PS/2 mouse, which can actually be converted between a traditional mouse and an upside-down trackball (which locks what was previously the mouse buttons, and turns them into feet!) The ball on the Trackpoint does not glide as smoothly as more recent trackball offerings (such as the Logitech Marble Mouse), but it works. I have several of these New In Box (bought for $7.99 each in 2014):

Capacitor Lists

Over the years, I noticed a strong smell of electrolyte coming from the rear of the computer after it had been running for about 20 minutes. In 2025, I finally decided to open it up and check the capacitors. There was a revision of the L40SX motherboard that had leaky round SMD capacitors all over, but my revision of the L40SX motherboard only had through-hole capacitors in the rear-right (under the floppy drive). Nonetheless, they were leaking, and I replaced them.

In 2026, I opened another one of my L40SX units, and discovered that it had the later 1992 revision, with leaking through-hole (green) capacitors scattered throughout the motherboard, in addition to the aforementioned through-holes in the upper-right. Generally speaking, these small radial green caps are 33uF 10V, and are in roughly the same position as the corresponding surface-mount (non-leaking) tantalums in the earlier revision. Therefore, I’m providing both lists of capacitors here. Note that the capacitors in the power supply area are largely the same, but the numbering has changed!

Revision Without Green Capacitors (1991)

Revision With Green Capacitors (1992)

Revised on October 4, 2026 (added alternate capacitor list)
Revised on October 13, 2025 (added Trackpoint section)
Revised on October 12, 2025 (added capacitor list)
Revised on December 21, 2019