This page describes the IBM SMS card "HGA", and is part of the SMS card database.

Function of the card:
Row Bit
Row bit

Part number: 373373

Customer Eng reference number: 734417

PCB number: 748403 , hole pattern: 490284

Used in: IBM 2821 Control Unit

IBM SMS card type HGA 373373 IBM SMS card type HGA 373373

Image courtesy of Henk Stegeman

References: National Museum of Computing.
IBM 2821 CCD, p88
This page created by Ken Shirriff on Wed Sep 15 18:15:10 2021.

The information on these pages comes from a variety of sources, especially old IBM documents on, as well as information from the IBM 1401 restoration team, especially Tim Coslet's SMS data and Jim Hunt's data. Much of this information was obtained through OCR, so don't expect complete accuracy. These pages are not associated with IBM in any way.