IBM Personal Computer/XT

Released 1981: The IBM Personal Computer/XT (model 5160, often shortened to PC/XT) is the second computer in the IBM Personal Computer line, released on March 8, 1983. Except for the addition of a 10 MB hard drive as standard, and extra expansion slots, it is very similar to the original IBM PC model 5150 from 1981. IBM did not specify an expanded form of “XT” on the machine or in documentation, but some publications expanded the term as “eXtended Technology” or just “eXTended”.

The XT was regarded as an incremental improvement over the PC and a disappointment compared to the next-generation successor that some had anticipated. Compared to the original IBM PC, the XT has the following major differences:

• Expansion slots increased from five to eight.
• Memory is increased to at least 128KB RAM.
• 10MB hard disk drive is included as standard equipment.
• PC DOS 2.0 included. (Offers a 9-sector floppy disk format, 180KB/360KB (single/dual-sided), compared to the 160KB/320KB provided by the 8-sector format of previous releases.)

The XT was not offered in a floppy drive-only model for its first two years on the market. At that time, in order to get a second floppy drive, the user had to purchase the 5161 expansion chassis.

I’ve written an own article about IBM PC DOS, see: The History of DOS

Expansion (ISA slots)
The number of expansion slots in the original IBM PC was a limiting factor, since needed components such as the video controller, disk controller and printer interface came as separate expansion cards and could quickly fill up the five available slots, requiring the user to swap cards in and out as tasks demanded. The XT addressed the problem by adding three extra expansion slots for a total of eight. While the slots themselves are identical to those in the original PC, the amount of physical space in the chassis differs, so two of the new slots cannot accept full-length cards. In addition, the spacing of the slots is narrower than in the original PC, making it impossible to install some multi-board cards.

Reception
The XT was well received, although PC DOS 2.0 was regarded as a greater improvement than any of the hardware changes, and by the end of 1983 IBM was selling every unit they made. The Compaq Portable also came out in March 1983, and would prove a popular competitor. It’s sometimes referred to as the “first PC clone”, but already before this, in June 1982, the Columbia Data Products’ MPC 1600 “Multi Personal Computer” was available. Other “clones” included the Seequa Chameleon, the Hyperion, Eagle Computer’s Eagle 1600 and the Corona PC. The latter two companies were sued by IBM and settled out of court, agreeing to re-implement their BIOS in a way that did not violate IBM’s copyrights. The IBM PC/XT was discontinued in the spring of 1987.

My IBM Personal Computer/XT

My IBM PC/XT came with a working 20 MB MFM hard drive and 640 KB RAM. I’ve noticed the floppy drive didn’t read diskettes reliable so I had to address that.

Floppy drive: I’ve removed the circuit board on the floppy to get to the reader heads and carefully cleaned the heads with alcohol and a cotton tip for a couple of minutes. I also lubricated the reader heads moving rail and some other moving parts for smooth action. After this the floppy drive seems to read disk reliable.