8 PIN DIN (DIN45326) FEMALE at the Monitor
The AT&T PC 6300 — a rebadged Olivetti M24 — outputs TTL-level digital RGB video through a DB-25 connector on the graphics card, running at a non-standard horizontal scan rate of 25.9 kHz (compared with the IBM CGA standard of 15.75 kHz). The Taxan Gold Card adapter bridges this DB-25 output to a standard CGA-style DE-9 connector and, simultaneously, to an 8-pin DIN (DIN45326) connector for Taxan monitors. Signals carried include digital RGB with an Intensity bit for a 16-colour palette, separate Horizontal and Composite Sync, Vertical Sync, and a proprietary TEXT mode signal.
| Pin | Name | Description |
|---|---|---|
| 1 | TEXT | Special TEXT signal (??) |
| 2 | R | Red |
| 3 | G | Green |
| 4 | B | Blue |
| 5 | I | Intensity |
| 6 | GND | Signal Ground |
| 7 | HSYNC/CSYNC | Horizontal or Composite Sync |
| 8 | VSYNC | Vertical Sync |
Signals
- TEXT — A proprietary signal associated with text-mode display; its exact function is not publicly documented.
- R — TTL-level Red video signal (digital, not analogue).
- G — TTL-level Green video signal (digital, not analogue).
- B — TTL-level Blue video signal (digital, not analogue).
- I — Intensity bit; combined with R/G/B it selects from a 16-colour palette, matching the Intensity scheme used in IBM CGA.
- GND — Signal ground reference for all video and sync signals.
- HSYNC/CSYNC — Horizontal sync or Composite sync (horizontal and vertical combined); the AT&T 6300 operates at 25.9 kHz horizontal frequency, which is non-standard and differs from the IBM CGA 15.75 kHz rate.
- VSYNC — Vertical sync signal.
Notes
- The 8-pin DIN connector on the monitor side is wired by the Taxan Gold Card adapter, which converts the AT&T PC 6300’s DB-25 video output.
- The AT&T PC 6300 is electrically identical to the Olivetti M24; the DB-25 on the graphics board carries TTL-level digital RGB alongside monitor-ID bits (ID0, ID1), a degauss signal, and +15 V power rails not present in this DIN connector.
- Because the horizontal scan frequency (25.9 kHz) differs from both IBM CGA (15.75 kHz) and EGA (21.85 kHz), standard CGA monitors are not compatible without the Taxan adapter or an equivalent converter.
- The function of pin 1 (TEXT) is not publicly documented; it is labelled tentatively based on available data.
References
- AT&T PC 6300 Service Manual — AT&T Information Systems / Bitsavers, primary service documentation for the AT&T PC 6300 (Olivetti M24 rebadge)
- Olivetti M21 M24 Theory of Operation (November 1984) — Olivetti Field Engineering Library, engineering document describing the M24 video sub-system and DB-25 display connector
- Colour Graphics Adapter Notes — John Elliott (seasip.info), documents standard IBM CGA DE-9 pinout and the Olivetti M24/AT&T 6300 deviation to DB-25