IBM Personal System/55

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IBM PS55 logo.svg
IBM PS55 Model 5550-T.jpg
PS/55 Model 5550-T
DeveloperIBM Japan
TypeProfessional Computer
Release dateMay 1987; 31 years ago (1987-05)
Operating systemJapanese DOS (K3.3 - J5.0)
PC DOS (3.3 -)
Windows 3.x
PredecessorIBM 5550

The Personal System/55 (パーソナルシステム/55) or PS/55 was a personal computer series released from IBM Japan in 1987.

The PS/55 was successor to IBM 5550 (Multistation 5550), but the machine was IBM PS/2 compatible, perhaps it was also an IBM clone. Most models had Micro Channel (MCA) for business use. Later, the AT bus model was released for home users.

Some models were exported to the United States.[2]

PS/55 Model 5550-T Booting-up


Display Adapter[edit]

Display Adapter II

Similar to IBM 5550, the text mode was 1040x725 pixels (12x24 and 24x24 pixel font, 80x25 characters) in 8 colors, can display Japanese characters read from font ROM. Graphics mode was 1024x768 pixels in 16 colors. It was the same resolution as 8514/A or XGA/A, but not compatible. These features were implemented in an MCA card called Display Adapter, and installed in the system unit.

The first Display Adapter was installed on the model 5570-S, also known as the first Micro Channel machine in PS/55, had a compatibility problem with PS/2. From the model 5550-S released in 1988, the Display Adapter II was installed that had been resolved PS/2 compatibility. In the boot sequence, display adapter enabled VGA on the motherboard and the video signal was output through MCA connector and display adapter. When using Japanese DOS, VGA was disabled and display adapter switched the video signal from VGA to own graphics chip. In addition, 256 color mode (1024x768 pixels in 256 of 262,144 colors) was supported.

Most models had compatibility with the Display Adapter II. VGA and following display modes were supported:

  • 1040x725 pixels with 80x25 characters in 8 colors or monochrome
  • 1024x768 pixels graphics in 16 colors or monochrome
  • 1024x768 pixels graphics in 256 of 262,144 colors

Later, XGA and VGA-only models were released. These machines couldn't run Japanese DOS (required DOS/V).

JIS layout keyboard[edit]

5576-002 Keyboard

Following keyboards can be connected to the PS/2 port. These keyboards (except A01) have new scancode set (81h, 82h, 8Ah) supports additional Japanese keys.


  • Tower
    • 5570-S/T/V (Early tower model. 5570-S, the first model of PS/55, didn't support English version of PC DOS and OS/2 because it wasn't 100% compatible with PS/2.[4])
    • 5580-Y/W (Late tower model)
  • Business Desktop (Predecessor to IBM PC 300/700 series)
    • 5560-W/N (Hi-end desktop)
    • 5550-S/T/V/W/N/Y/L/R (Mainstream desktop)
    • 5540-T (Low-end desktop)
  • For small business, home users
    • 5530-Z/S/T/U/W (Desktop with integrated a display, Predecessor to PS/V Vision)
    • 5510-Z/S/T (VGA model. Predecessor to PS/V)
  • Laptop
  • A4 Notebook
    • PS/55note (Predecessor to ThinkPad. AT bus or MCA bus.)
  • Rebranded IBM 5550
    • Model G~P (1987-1991)


See also[edit]


  1. ^ "マルチステーション、PS/V、PS/2、PS/55の一部保守活動中止の発表" [Some model of Multistation, PS/V, PS/2, PS/55 End of Life Announcement] (in Japanese). IBM Japan. Retrieved June 7, 2016.
  2. ^ "IBM PS/55TMの最上位モデルを発表 - Japan"(September 26, 1988), Retrieved June 7, 2016
  3. ^ "IBM 20万円を切った低価格DOS/V専用パソコン登場"(May 7, 1991), Retrieved June 2, 2016
  4. ^ 'ASCII EXPRESS:日本IBMがIBM PS/2互換の80386マシン3機種を発表 英語版OS/2用アプリケーションもすべて動作可能に'.ASCII June 1988, Ascii

Further reading[edit]

  • IBM Japan (1990). IBM PS/55ハードウェア モデル5550-S/T/V技術解説書 [IBM PS/55 Hardware:Model 5550-S/T/V Technical Reference]. Ohmsha. ISBN 4274076245.

External links[edit]