IBM Personal System/2 Laptop 40 SX (PS/2 L40SX) Notes
The L40 SX was announced
March 26, 1991. Here are some highlights
from the announcement letter:
- 20Mhz 80386SX CPU
- 2MB of 80ns memory expandable to 18MB
- 60MB hard drive
- 3.5" 1.44MB floppy drive
- VGA resolution LCD (10 inches, Supertwisted Nematic LCD, 640x480)
- Ports: Serial, parallel, keypad/mouse, external VGA monitor, and
an expansion connector.
- 17 key external numeric keypad
- Socket for an 80387SX numerical co-processor
- Included accessories: AC adapter, rechargeable battery pack and a
- Weight: 7lbs, including the battery.
The machine was targeted at mobile professionals with an initial price
of $5995 for the base model without options, which would be over
$11,300 in 2020 equivalent dollars. To put things in perspective, a
base model 1991 Nissan Sentra had a manufacturer's suggested retail
price of $8290. The 2MB memory upgrade started at $899, while the 8MB
memory upgrade was an eye-popping $3595.
- Data and fax modem (2400 bps for data, 9600 bps for fax, Hayes
- A second serial port
- Trackpoint pointing device (can be used as a trackball or a mouse)
- 2, 4, or 8MB memory upgrades
- Quick charger
- Car power adapter
Prices dropped several times during the life of the machine:
On July 9th, 1992 IBM withdrew the PS/2 Model L40 SX from marketing,
making it available for sale for a little over 15 months.
- 1991-07-25: $5245
- 1991-10-02: $3955
- 1991-11-19: $3645
- 1992-02-11: $2495
- 1992-05-02: $1965
Here are some things to keep in mind with these machines:
There are three batteries on these machines:
- A large NiCD battery pack for portable use of the machine. These
are all probably dead now and should be rebuilt with NiCD cells if you
are going to try to use the machine as a portable machine.
- A CMOS battery to preserve the CMOS settings while the machine is
powered off. The original (and correct) battery is a Panasonic BR-2/3A
which is a 3 volt Lithium battery, available from Digikey for around $5
USD. Do not use a CR-123A photo battery; the size and voltage are
fine but it will not last as long.
- A memory standby battery which is a 3.6V NiCD pack rated for
The machine will run fine if this battery is dead but you will not be
able to swap the main battery without this battery functioning. (I only
use the machine when connected to AC power so this is not an issue for
IBM originally sold the machine with a 60MB Conor hard drive.
Surprisingly, the hard drive is a standard 2.5" IDE mobile drive. If
you find a machine with the original hard drive you can assume it is
dead; I've only seen one surviving original hard drive.
While the hard drive is a standard IDE hard drive, the ribbon cable
that connects the drive to the motherboard is not standard and it is
very fragile. Be careful working with it.
If you have to replace the hard drive don't use a mechanical hard
drive. Use a Disk-On-Module or an industrial Compact Flash card. See "Upgrading
an IBM L40 SX to an SSD" for the procedure.
The standard machine came with 2MB of memory on the motherboard. Two
memory slots allow for expansion to a maximum of 18MB. The memory is
not standard so you have to find the exact part numbers. The memory
upgrades were expensive options so finding a machine with a lot
additional memory is unusual.
Communications Cartridge I
The Communications Cartridge I (model
3541-001, 06G8050) is an option
that allows one to use the L40 SX to connect to midrange or mainframe
computers. The device itself is a self-powered bus expansion that holds
one short 8-bit ISA card and connects to the L40 SX using a thick
cable. Originally intended for use with Token Ring adapters, 3270
emulation cards or 5250 emulation cards, it also can work with other
ISA cards such as Ethernet or SCSI cards.
The announcement letter for the L40 SX indicated that an option like
this would be available. It was finally announced on October 17th,
1991. These were originally priced at $595 so you won't find too many
in the wild.
Cards known to work:
- IBM Token Ring (PN 25F7367), from the announcement letter
- IBM 3270 (PN 53F6425), from the announcement letter
- IBM 5250 (PN 49F5618), from the announcement letter
- Generic NE1000 Ethernet card, tested personally
- Future Domain TMC-850IBM SCSI card, tested personally
- The connectors are consist of two rows each with 60 pins. Both
end of the cable are male. The cable side mail connectors look to be
AMP 6-175473-1 and the device side female connectors look to be AMP
circuit board, top view
circuit board, bottom view
Here are some resources that you will find useful for your L40 SX.
(Special thanks to John Roth who provided the paper marketing brochure,
the keyboard templates, the L40 SX Presentation guide, and the
Communications Cartridge instructions.)
IBM provided blank templates that you
could write on to remind yourself of the special key combinations of
programs you were using. (Right click to save the full sized image.)
IBM announcement letters:
These are a standard 1.44MB diskette images. You can create a
diskette from these images using dd (Linux), WinImage (Windows), or DskImage
Created August 16th, 2020, Last updated November 26th, 2020
(C)opyright Michael B. Brutman, mbbrutman at gmail.com