WINPCP

Windows 3.0/3.1 Display Driver for Plantronics Color Plus and other supported clone CGA video Cards at 640x200x4 colors.

WINPCP is a custom Windows 3.0/3.1 display driver targeting Plantronics Color Plus–compatible graphics hardware, providing 640×200 resolution with 4 colors (2 bpp) using the classic CGA-style interleaved video memory layout.

WIN = Windows
PCP = Plantronics Color Plus

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Project Goals

• Implement a fully functional Windows 3.0/3.1 display drivers for:
  • Plantronics Color Plus
  • Twinhead CT-6190G
  • VTECH CGA/MDA cards with VTCL 27-0739-01 chip
  • ATI Small Wonder
• Support:
  • 640×200 resolution
  • 4-color (2 bpp) graphics using two 1-bpp planes
  • Correct CGA even/odd scanline interleave
• Behave compatibly with stock Windows 3.0 GDI expectations
• Run on real vintage hardware, not just emulators

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Hardware Target

Known / expected compatible hardware includes:

• Plantronics Color Plus
• Twinhead CT-6190G series
• Yamaha V6355-based CGA/Plantronics-compatible cards
• VTECH CGA/MDA cards with VTCL 27-0739-01 chip
• ATI Small Wonder
• Other CGA-derived cards supporting Plantronics memory banking

Video memory model (per plane):

B800:0000  plane 0, even scanlines
B800:2000  plane 0, odd  scanlines
B800:4000  plane 1, even scanlines
B800:6000  plane 1, odd  scanlines

Scanline stepping follows the classic CGA pattern:

• even → odd: +2000h
• odd → even: +2000h + wrap correction (+80A0h)

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Technical Approach

This driver is being developed using a hybrid reference strategy:

• Behavioral contract
  • Windows 3.0 CGA.DRV
  • Windows 3.0 TANDYDSP.DRV
• Hardware truth
  • GEM Plantronics driver (pla_drv1.a86)
  • Plantronics Color Plus hardware documentation
  • Empirical testing on real hardware

Text rendering, BitBlt, and fills are implemented by expanding pixels into two 1-bpp planes, using masked replace operations:

dst = (dst & ~mask) | (mask & fill)

Foreground and background colors are mapped per plane using 00h / FFh fill bytes derived from GDI draw modes.

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Current Status

🟡 In development

High-level progress:

• Hardware memory layout confirmed
• CGA interleave stepping verified
• Text glyph expansion logic reverse-engineered from TANDYDSP
• Driver Enable / Disable skeleton
• Core VRAM primitives
• BitBlt / PatBlt
• ExtTextOut (text rendering)
• Cursor support
• Final integration and testing

This repository is being built incrementally, with correctness prioritized over speed.

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Repository Layout

WINPCP/
docs/
notes/          Development notes and reverse-engineering findings
references/     Public or user-provided reference material
src/
drv/            Driver source code
inc/            Headers, constants, and shared definitions
build/          Build scripts and toolchain notes
tests/
dos/            DOS-side hardware and VRAM tests
win3/           Windows 3.0 test applications

Licensed or proprietary materials (e.g., full Windows DDK distributions) are not committed to this repository.

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Build Environment

Planned build environment:

• MS-DOS
• Windows 3.0 DDK
• MASM + LINK (period-correct toolchain)

Exact build steps will be documented once the driver skeleton is in place.

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Why This Exists

Windows 3.0 never shipped with native support for Plantronics Color Plus graphics and video card Manufactures did not provide drivers for their compatible cards.

WINPCP exists to:

• Preserve and document this hardware
• Enable historically accurate Windows environments
• Provide a clean, well-documented example of a non-VGA Windows display driver

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Status Disclaimer

This is a retro-computing research project.

Expect:

• incomplete features
• temporary hacks
• verbose documentation
• a strong preference for clarity over cleverness

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License

To be determined.
Likely a permissive license covering original source code only.

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Acknowledgements

• Microsoft Windows 3.0 DDK
• GEM / Digital Research Plantronics drivers
• The vintage PC and retro-computing community
• Real hardware testing (the only truth that matters)