Windows 3.0 on CGA

160 × 100 pixels. Sixteen RGBI colors. A compact Windows desktop.

Download CGA.ZIP · Install · How it works · Driver source

Paintbrush, meet CGA. The landscape itself uses all sixteen colors.

The driver uses CGA's text-mode circuitry as a sixteen-color framebuffer for Windows 3.0. Tiny bitmap fonts and compact controls make room for actual windows on a screen just 100 pixels tall.

This repository is the CGA front door for Windows XT / oemdisplay-tandy. The current driver, installation package, development and support live there.

Get it running

You need an IBM CGA-compatible RGBI display path, an installed Windows 3.0 that can run in real mode, DOS 3.3 or later, and 640 KB of RAM. The qualification target is an IBM XT with a 4.77 MHz 8088 and IBM CGA. You supply DOS and Windows; the download supplies the drivers, fonts, grabber, artwork and helpers. Windows 3.1 is unsupported.

1. Download CGA.ZIP and extract it. Keep root SETUP.EXE, README.TXT and the complete CGA folder together. Transfer that extracted folder to your DOS machine by your usual method.

2. Exit Windows completely. From the extracted folder, run:

   SETUP C:\WINDOWS 100

   Use your actual Windows directory. Wait for the success message; installation takes several minutes on a 4.77 MHz 8088.

3. Change to your Windows drive and directory, then start WIN /R.

That's the fixed 160 × 100 desktop. For a larger desktop, use PAN in place of 100 during installation. Setup installs PAN automatically. A previous OFF choice is preserved; run PAN inside Windows to enable it again. Everything needed for installation runs on the DOS computer; no Python, modern-PC preparation or individual support-file hunt is required.

Full CGA install guide · Current release and checksums

Choose a display mode

One download contains four choices. Exit Windows and rerun Setup to change modes.

Setup choice	Windows desktop	What the CGA screen shows
100	160 × 100, 16 colors	The complete desktop, with compact fonts and controls
PAN	320 × 200, 16 colors	A movable 160 × 100 viewport into the larger desktop
320	320 × 200, 4 colors	Black, bright cyan, magenta and white
640	640 × 200, 2 colors	Black and white

More desktop than screen

Viewport panning is included in the current public package. Install it with:

SETUP C:\WINDOWS PAN

In PAN, Ctrl+Alt+arrows moves the view, Ctrl+Alt+Home returns to the top left, and Ctrl+Alt+End reveals the active window's bottom/right. Edge scrolling and following the active window help reach controls outside the view. Queued commands are applied after busy drawing finishes.

Open Panning settings with Ctrl+Alt+S, or run PAN /SETTINGS inside Windows. Apply saves settings; Cancel discards unapplied edits. Horizontal steps round up to multiples of eight pixels. See the illustrated panning guide.

In fixed 100 mode, those movement shortcuts move windows and active client contents to expose hidden controls; the framebuffer remains 160 × 100. Fixed 320 and 640 can opt into a window workspace through PAN.

Paintbrush on the larger desktop, viewed through the same little screen.

How it works

Ordinary CGA graphics offers 320 × 200 with four colors or 640 × 200 with two. CGA text attributes, however, can select from the full RGBI palette: red, green, blue and intensity.

The 160 × 100 driver programs the CRTC for 80 columns and 100 short character rows, with two scanlines per row. Every cell contains the right-half-block character (DEh). Its background paints the left logical pixel; its foreground paints the right. Disable blinking to make all sixteen background colors available, and each cell becomes two independently colored pixels.

80 × 2 = 160 pixels across. 100 rows = 100 pixels down. All sixteen colors.

Windows draws through the display driver's four-plane shadow bitmap in RAM; the driver converts the result into character/attribute pairs in CGA memory. The color comes from RGBI text attributes, without composite artifact color. VRAM accesses temporarily disable video to avoid CGA snow; visible blanking and physical-card behavior still need hardware qualification.

For the details, follow the conversion implementation, mode setup and implementation record.

Tiny windows, real captures

Notepad: a File Open dialog in 100 pixels	File Manager: a little room to browse

Classic CGA: 320 × 200, four-color mode	640 × 200, monochrome

These are existing native Windows emulator captures. The fixed-mode images are unretouched decodes of saved CGA video memory; the enlarged versions repeat pixels. The panning image retains the emulator's frame and border. They are not physical-hardware photographs. The Paintbrush landscape matches all 3,840 pixels of its input picture and uses all sixteen colors within the picture. Capture provenance and originals.

Experimental, with receipts

The recorded runs use IBM XT/CGA emulation with 640 KB and CGA snow enabled. Coverage includes installation and recovery, compact dialogs, Paintbrush, viewport boundaries, off-screen drawing and queued panning controls. Physical cards, clone CRTCs and composite output remain unqualified; PCjr, Tandy and EGA/VGA are separate targets. Extended characters in the compact 160 × 100 fonts currently use fallback boxes.

To undo, exit Windows and run this from the retained package folder:

SETUP UNDO C:\WINDOWS

Follow the package's README.TXT for recovery. The explicit RESTORE command restores whole saved INIs and can lose later INI edits.

Follow the wires

• Canonical source and support — report problems and contribute driver changes there.
• CGA qualification records · CGAPAN evidence · Shared panning evidence.
• Other hardware — the rest of the Windows XT family.
• Component notices — original fonts and helpers retain their licenses; adapted Microsoft/DDK components retain their own notices.
• Front-door verification record — the source revision and public package checked for this page.

Windows 3.0. 160 × 100. Sixteen RGBI colors.