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The Videx VideoTerm was the 80-column card that turned the Apple II into a business machine. Emulating it on an FPGA means reverse-engineering a 1981 MC6845 CRTC design and understanding why slot 3 is unlike every other slot in the machine.

Part 1 of 2. This part covers the Videx VideoTerm’s hardware architecture, the MC6845 CRTC, and why slot 3 is architecturally special. Part 2 covers the rendering pipeline, C8 ownership, and the Pascal boot hang.

In 1977, the Apple II shipped with 40 columns of text. That was fine for BASIC programs and games. It was not fine for WordStar, VisiCalc, or the CP/M business software that was reshaping the industry. A serious word processor needed 80 columns. A spreadsheet with real data needed 80 columns. Anyone who wanted to use an Apple II for actual work needed 80 columns.

The Videx VideoTerm, introduced in 1980 and manufactured in Corvallis, Oregon, was the card that solved this problem — and dominated the market until Apple built 80-column support into the IIe in 1983. It was the most widely supported 80-column card for the Apple II and II+, compatible with Apple Pascal, WordStar, and virtually every serious business application of the era. Understanding why it worked the way it did requires understanding a chip that has largely faded from memory: the Motorola MC6845 CRT Controller.

Before getting to the Videx card itself, it helps to understand what Apple II video actually looked like.

The Apple II+ outputs NTSC composite video — a single analog signal designed for 1970s consumer televisions. It works, in the sense that you can see the screen. But NTSC composite has color bleeding, chroma artifacts on text, and a horizontal resolution that is fundamentally limited by the bandwidth of the signal. The 40-column text mode that the stock Apple II produces is legible on a period-correct TV. On anything else it is a reminder of how much display technology has changed.