IBM PC Convertible 5140

In 1986, IBM shed the light on the IBM PC convertible. Lighter and smaller than the IBM PC portable, this new device set the tone for generations to come, and is in fact IBMs first ever laptop computer.

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Historic Overview

Just two years aftet the IBM PC portable, IBM introduced the PC convertible, which took upfront developments and refinments seen in later generations.

IBM PC Convertible 5140

This device marked many technology advancements for IBM, as it was the first to use the newly deviced manufacturing process for logic boards using surface-mount components. It was also the first IBM computer to be equipped with two 720 KIB 3.5 floppy drives by default. And it was the first that could run off batteries, supporting power management functions, so the system could essentially be put to sleep and resume from its last state. This was made possible by using a special version of the Intel 80C86, which had a static core. Suspending would essentially simply halt the CPU clock, and resume the clock if powered up again. This would of course only work while connected to a fixed power source, or while running off a charged battery.

The PC convertible also sort-of took upfront the docking idea. Essentially, the built-in display could be easily detached from the base unit. With the LCD detached, the base unit could be put under a regular size CRT monitor, still allowing to use the built-in keyboard. One would prefer to use a CRT anyway, as the built-in LCD offers only a skeewed resolution and doesn’t offer good readibility.

The PC convertible is expandable, but uses proprietary modules, which snap to the backside. Besides the two floppy drives no option forĀ  a built-in hard drive was given. Also, no standard-type connectors for serial and parallel ports exist, these had to be added using a proprietary expansion module. This imposed quiet a lock-in to the users, as they couldn’t expaned the unit with off-the-shelf components.

Although the PC convertible didn’t officially belong to IBMs PS/2 line, its design closely resembles the later PS/2 design. And so it was propably also doomed by the very same decision to put a lower-end CPU into the PS/2 machines. As history has it, the PS/2s where crippled in order to not jeopardize IBMs mainframe division by offering only less powerful machines into the mass market.

This widely opened the door to clone vendors, as they where of course not bound to this artificial restriction. In fact, the IBM PC convertible, apart from it’s form factor, power management, and better portability, didn’t offer much difference to it’s predecessor, the IBM PC portable. Yes, it was lighter, it was less bulky, but performance-wise, it was pretty much the same computer at its heart.

Essentially, IBM drove their own customers away by forcing users into buying proprietary expansion modules, yet offering sub-par performance at a rather high premium, while competing against better and less expensive clones at the same time. So despite some innovative features, the IBM PC convertible is generally considered a market failure.

Specs

The PHINTAGE Collection currently holds an IBM PC convertible.

Vendor International Business Machines Corporation
Model PC convertible 5140
Released 1986
Original Streetprice 2000 US$
Weight 5.7 KG
Dimensions
Builtin Display Yes, monochrome 80×25 lines LCD
Builtin Battery Yes
CPU Intel 80C88 @ 4.77 MHz
RAM 640 KiB
Storage
  • 2 3.5″ 720 KiB floppy drives
Network Support no
USB no
Video Output yes (via expansion module adapter)
Other 1 proprietrary expansion port connector on the back
Operating System IBM PC-DOS
Overall Condition
  • very good condition, fully working
  • some minor scuffs and scratches
  • no battery
Restoration Parts needed
  • replacement battery
  • expansion modules (any)

Gallery

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