Olivetti M24-family 640x400 Support List Version 20261102.2 Initially prepared by trixter@oldskool.org, contributions by many others Coordinating forum thread: https://forum.vcfed.org/index.php?threads/coordinating-m24-family-high-res-640x400-graphics-mode-support.1259653/ === Intro The Olivetti M24 (and OEM rebadges, such as the AT&T PC 6300, Xerox 6060, and Logabax Persona 1600) introduced an enhanced CGA mode that doubled the monochrome resolution from 640x200 to 640x400. While the M24 sold well in Europe, the rebadged AT&T 6300 was successful in the USA, and this success prompted many USA-based software manufacturers to add support for the 640x400 mode in their software. A few years later, other manufacturers such as Toshiba were prompted to add support for the same mode in their BIOS, under the same Int 10h, mode 40h setting. What follows is a compilation of software titles that support this enhanced CGA mode, which this document will refer to as "M24's 640x400 mode" in reference to the first system to popularize it. If you know of any additional titles, contact trixter@oldskool.org or mobygamer@gmail.com to have them added to this list, and the software added to this archive. Note: Olivetti and AT&T marketed a "Display Enhancement Board", or DEB, that doubled the RAM and added 16-color graphics mode in 640x400, along with text/graphics overlay features. The DEB is exceedingly rare, and hardly any were sold, so there is very little support for its extra capabilities. This list is primarily concerned with the more common and better-supported 2-color 640x400 mode, but if any titles have extra DEB support, that will be denoted as well. A note on homebrew/fan 640x400 2-color patches: The rise of homebrew and AI-assisted development have led to fan patches or rewrites of games, and well-meaning fans sometimes implement M24-family 640x400 2-color support as part of the work. However, M24-family monochrome monitors support 16 grayscale shades to represent all 16 possible CGA colors, so they already do a good job of representing 4-color CGA in monochrome. In such cases, dithering 320x200x4 to 640x400x2 actually makes the graphics look worse. Titles that do not provide enhancement beyond simple 320x200x4 -> 640x400x2 dithering will not be included in this list, as they are considered a downgrade of the original experience. True opportunities for 640x400 enhancement occur when a software title falls into these categories: - Onscreen graphics are primarily rasterized from vectors, ie. "drawn from scratch". Examples: Sierra AGI and SCI games, Microsoft Flight Simulator, spreadsheet graphs and charts, Fractint - The title has high-res assets that cannot be represented well at 320x200 or 640x200 resolution. Examples: Microsoft Windows, Geoworks Ensemble - The title has no CGA support at all, and would not otherwise run on an M24-family system. In these situations, 640x400 support is indeed an enhancement, and such titles will be included in this list. === Confirmed titles, and how to activate 640x400 support Applications: - Lotus 1-2-3 (version 2, other versions might also have support): Select during installation - Microsoft Word for DOS 4: Autodetects. If autodetection fails, "SET OLIVETTI = true" in DOS environment before running. - Microsoft Word for DOS 5 (Requires ROM BIOS 1.43): Select during installation Environments: - Geoworks Ensemble 1.0 and 1.2: Select during installation. (Note that Geoworks Ensemble 1.0 will not start on an M24 system if the CPU has been swapped out for an NEC V30; it also does not support the M24-specific AT&T/Logitech "keyboard mouse".) - GEM (versions 1 through 3, possible others): Select during installation - Microsoft Windows 1: Select during installation - Microsoft Windows 3.0: The Olivetti-specific distribution has support for 640x400, keyboard-attached mouse, keyboard; select with SETUP.EXE - Microsoft Windows 3.1 beta 3126 (the last one to support real mode): Properly detects Olivetti display hardware in the setup Games: - All Sierra SCI games (1989, Anders M Olsson's "ATT320.DRV" driver): Copy the files from the driver distribution into the game directory, then run INSTALL.EXE and pick "AT&T 6300 640x400 - monochrome" from the list. If the game is already installed, modify RESOURCE.CFG to point to ATT320.DRV. - Fox Oring v1.1 (2025, Yevgeniy R. Sova): Select "O" at title screen - Spacewar v1.71 and v1.72 (1986, Bill Seiler): Run SWATT.EXE for 640x400 support - The Colony: Autodetects Graphics: - Compushow (graphics viewer) - Dr. Halo II: Select "AT&T DEB" during setup, then pick "640x400 2-color" for the graphics mode. - Dr. Halo III: Select "AT&T Indigenous" during setup for M24 family; select "AT&T DEB" for the DEB. - FRACTINT: Use "t" to select the rendering video mode; scroll down the list to find "AT&T 6300" - PC Paintbrush 1.68: Run PCINSTAL to select and copy M24 support to the local installation. Can supposedly capture 640x400 screens as well. - Pizazz Plus (Screen capture and printing): Autodetects Miscellaneous: - MetaWindow graphics library titles 3.3B and later: Supports DEB 16-color. Background: Some Norwegian point-n-click edutainment games from 1989-1990 (one example: https://archive.org/details/alice-eventyrspill) were produced with this library and support DEB/Olivetti 16 color mode if you edit the .bat file (use set grdev=/a:3 instead of set grdev=/e:4) as it is set to launch with EGA mode by default). - Microweb (web browser) Programming/Compilers: - GWBASIC (Olivetti/AT&T versions distributed with M24/6300 MS-DOS 2.11 or 3.x): SCREEN 100 will go into 640x400 mode. - Microsoft Quickpascal: Ensure "ATT6300.VID" is distributed with your programs - Turbo Pascal version 4 through 7: Ensure you distribute ATT.BGI with your programs, and also give the user a way to select AT&T mode, as it isn't detected via detectgraph() Utilities: - Customer Diagnostics (Olivetti/AT&T/Xerox): Built-in support, and can also trigger the degaussing circuit of an attached monitor. === Partial/Debunked support - As-Easy-As v5.70 (Lotus 1-2-3 clone): Use /ATT or /ATT2 (manual is ambiguous) to specify 640x400 for graph generation. Program will not launch properly without one of these options. However, the program doesn't seem to have actually been tested on an M24 system, because it uses high-intensity background colors that, on an M24 system, blink annoyingly. - Checkers v1.61 (1990, Judson S. McCranie): Includes ATT.BGI but has no way to select AT&T support (autodetect does not work) - Connect 4 v1.1A (1989, Judson S. McCranie): Includes ATT.BGI but has no way to select AT&T support (autodetect does not work) - Earl Weaver Baseball: No version supports 640x400, but the introductory crack screen on one of the pirated versions does. - Simon (2025, Yevgeniy R. Sova): Game initializes graphics mode correctly but then crashes with "Overflow in module SIMON" - Windows 3.0 DEB 16-color driver (retrogcom): Available from https://github.com/retrogcom/windows-3.0-egc and as of 2026 is in active development. === Unconfirmed - Dr. Halo II and III have setup options for the AT&T DEB - FRACTINT: DEB support is mentioned - All previously mentioned operating environments (Microsoft Windows, GEM, Geoworks Ensemble) are supposed to support the DEB. Windows 2.03 in particular has a DEB display option. === Additional hardware and emulator support for 640x400 There were non-M24 other systems that provided a 640x400 mode under the same Int 10h BIOS video mode 40h: - The Toshiba T1200XE - Olivetti M290 with GO481 card On such systems, the 640x400 mode works like it would on any M24-family system, even though it may not be strictly detected as such. Some systems have physical hardware support for the mode, but lack BIOS support for it: The Zenith eaZy PC has the NCR CGMA chip with 32K of video RAM and a 640x400 display, but even though the Windows 3.0 installer suggests using the AT&T PC6300 640x400 monochrome graphics driver, it doesn't work. See https://youtu.be/zPdKIrVV-fU?si=Pcr0Ud-0RCEyPXfb&t=848 for a demonstration. Some later Olivetti-manufactured systems that support VGA, such as the M240 (AT&T 6300 WGS), also support 640x400, but only using the VGA card they shipped with. That card contains a Paradise PVGA1A-based chipset with a custom BIOS that looks for attempts to initialize mode 40h (the 640x400 mode), and passes those through to the host system's BIOS, which retains the original 640x400 support. As of 2026, this is the only known way of producing the M24 640x400 mode through a VGA connector. Emulators that claim to support the M24 640x400 graphics mode are 86Box, PCem, and MAME. Support for the DEB was added to 86Box, with these notes: "Settings -> Display -> Configure on the internal video "Olivetti M21/M24/M28 (GO317/318/380/709)". There's a new checkbox right after "RGB type": Display Enhancement Board (GO329). Tick the option and boot DOS with DEVICE=DEDRIVER.DEV in CONFIG.SYS." === Works in progress https://www.mobygames.com/attributes/attribute/1985/ is a list of games that support M24's 640x400 mode; it's mentioned here in case more games get added to it in the future.