Editing IBM 3270 PC Maintenance Guide (section)

== Card Inventory at Service Time ==

For each service visit, verify the card complement and check the as-built ROMs:

# '''Keyboard Adapter''' — Two ROM variants: '''6323581''' (simple) or '''6323582''' (complicated with NMI + serial). '''Critical: this card holds the video BIOS''' for the 3270 PC Display Adapter. Without it, the video cards do nothing.<ref>http://www.seasip.info/VintagePC/5271.html</ref>
# '''3270 PC Display Adapter''' — SCN2672 PVTC at 0180h–019Bh. Inspect the SCN2672 socket for oxidation.
# '''APA card''' (where fitted) — adds CGA modes + 3270-PC graphics modes.
# '''PSS card''' (where fitted) — Programmed Symbol Set, RAM-loaded fonts.
# '''3278/79 Emulation Adapter''' — I/O at 2D0h–2D6h (older) or 2D0h–2D7h (newer). BNC twinax to controller.