IBM AT 5170

"IBM 5170 -The Birth of the AT Standard"

Introduced in August 1984 and discontinued in 1987, the IBM Personal Computer AT (Model 5170) established a new benchmark in the 1980s computing market. Shortly after its release, it became widely imitated by other PC manufacturers. Powered by the 16-bit Intel 80286 processor, the IBM AT introduced significant innovations, including EGA graphics, 16-bit expansion slots, and a 1.2MB 5.25" floppy disk drive. In April 1986, IBM refreshed the AT by upgrading the CPU from 6 to 8 MHz.

• Total Units Sold: Over 100,000
• Initial Price: $6,000 (approx. $16,700 in 2024 money)

IBM 5170 AT A GLANCE

• Operating System: PC-DOS 3.0 (Compatible with MS-DOS up to 6.22)
• Processor: Intel 80286-2 @ 6.0 MHz or 8.0 MHz
• Chassis: Full-sized case with 8x ISA expansion slots and 3 drive bays (2x FDD, 1x HDD)
• Memory: 512 KB RAM (Expandable to 16 MB via expansion cards)
• Firmware: Built-in Cassette BASIC for system setup and fallback booting
• Graphics: EGA (16 colors, backward compatible with CGA and Hercules)
• Floppy Drive: Built-in 1.2MB 5.25" (Y-E Data YD-380)
• 3.5" Floppy Support: 720KB supported; 1.44MB supported on later models
• Hard Disk: 20/30 MB (CMI 6426-S)
• Keyboard: Originally shipped with 84-key Model F; later models included the 101-key Model M
• Built-in keylock on the front (disabling keyboard)

IBM AT 5170 models

IBM released several versions of the 5170, with three primary motherboard types and multiple sub-models.

Notes

• AT probably means 'Advanced Technology'
• The latter 8MHz AT revision featured a 16-bit MFM controller

IBM AT 5170 Motherboard Variations

• There were 3 main motherboard variations

IBM AT 5170 Sub-Models

• These are the sub-models:

Operating System & Set-Up

The IBM 5170 primarily used PC-DOS 3.0, with compatibility extending to:

• MS-DOS 1.0 – 6.22
• OS/2 1.x, XENIX
• Microsoft Windows 1.0 – 3.1

Setup Methods (3 Options)

When you add any device, the IBM 5170 needs a setup. These are the three different setup methods:

1. IBM AT Diagnostics (5.25" bootable setup disk -more information here)
2. 3rd-Party GSETUP Utility (on floppy disk -more information here)
3. Cassette BASIC Setup (manual code input, no disk required -more information here)

Graphics and Cards

The IBM AT pioneered support for EGA (Enhanced Graphics Adapter) via expansion cards:

• EGA: 640×350 resolution, 16 colors (64-color palette)
• CGA: 640×200, 4 colors
• Hercules: 720×348 monochrome
• MDA, PGA also supported

Audio Capabilities

Out of the box, the IBM AT featured only a PC speaker, mounted on the front panel.

• Adlib, Sound Blaster, or compatible cards can be added for enhanced audio.

IBM 5170 I/O Ports, Sockets, and Switches

• Keyboard Port: AT-style (rear), also supports XT keyboards
• RTC: Motorola MC146818 (with CMOS memory for BIOS settings)
• Math Co-Processor Socket: Supports Intel 80287
• Switches: No DIP switches; includes a display type switch

IBM 5170 Monitors

The IBM AT came with an EGA color monitor supporting CGA and Hercules modes:

• IBM 5154 (EGA, color – also supports CGA and Hercules)
• Other options: IBM 5151 (green monochrome), 5153 (CGA), 5175 (PGA)
• VGA cards allow for modern CRT/LCD/TFT monitor connectivity
• Display type switch on the motherboard allows EGA/CGA/MDA mode selection

Expansions & Upgrades for the IBM AT

Basic Upgrades (for its time)

• A 128K memory upgrade to 640K (standard for its time, requires a memory expansion card)
  • IBM 128K/256K/512K Memory Module Kit
• Math co-processor chip, the Intel D80287 (available socket inside)... running at 6, 8, or 10 MHz
• 2nd internal Floppy Disk Drive (All 5170 models can handle 720KB 3.5 drives, but only later revisions can easily handle 1.44MB 3.5 drives)
  • For placing any 3.5 drive... You need a 5.25/3.5 case plus an IDC adapter (Edge connector to 34-pin IDC floppy adapter) and a Molex cable (Molex male to FDD female)
• Adlib sound card (more here: Adlib Sound Card)
• Game card for adding 2 x 15-pin joysticks

Modern Upgrades

• Up to 16MB memory upgrade (requires a memory expansion card)
  • Intel Above Board
  • AST Rampage
  • AST Advantage Premium
  • BRAT90
  • BocaRAM AT
• VGA graphics card (works fine with all monitors)
• Soundblaster sound card (or clones)
• IDE Hard Disk based on a CF/SD card -Depending on the card, you may need to upgrade your BIOS
• Gotek USB drive (Needs the same adapters as any common 3.5 FDD, check above)
• ROM upgrade (more here)
• RTC replacement (6V can be achieved with a case of 4x1.5V batteries) -Note that you need to go through the Setup Procedure explained above

■ IBM 5170 AT Computer

BinaryValue.com (c)

Video Tutorials:

• https://www.youtube.com/watch?v=yyL_a9QE8ag

Sources:

• https://en.wikipedia.org/wiki/IBM_Personal_Computer_AT
• https://minuszerodegrees.net/
• https://retrocmp.de/ibm/5170/5170-t3.htm
• https://ancientelectronics.wordpress.com/2021/06/28/ibm-at-5170/
• https://www.dosdays.co.uk/computers/IBM%20PC-AT%20(5170)/ibm5170.php
• https://www.pcjs.org/machines/pcx86/ibm/5170/