MDA stands for Monochrome Display Adapter, and it was introduced by IBM alongside the original IBM PC in 1981.

As the name implies it is monochrome. It was normally used in combination with a green or amber display. Moreover, it can only display text and characters from the built-in font in 80 columns and 25 lines with a font size of 7x11 (in a 9x14 'box'). The only extras that it has are underlined text, bright text and reverse video. The vertical refresh of MDA is only 50Hz, but with the phosphor glow of green and amber monochrome monitors this was not noticeable.

The main selling feature of this adapter, compared to CGA, was its clarity as it uses effectively a 720x348 resolution, which made it very popular for business software. For games, you’re going to be limited to text mode games, like text adventures.

This mode can be set using machine=mda in your DOSBox-X config file. Video memory is fixed to 4KiB and cannot be changed.

You can optionally change the display colour by setting in the [render] section of your config monochrome_pal= to "green", "amber", "white" or "gray". Or you cycle between them with CTRL-F7.

CGA stands for Color Graphics Adapter, and like MDA was introduced by IBM alongside the original IBM PC in 1981.

As the name implies, it supports colour, and unlike MDA, it supports drawing to the screen which made it popular for games. Due to the higher price of the adapter and monitor, and the lower resolution, it was less popular for business use than MDA and later Hercules. Also note that CGA is not backward compatible with MDA. The vertical refresh of CGA is 60Hz, which matches up well with the majority of modern 60Hz LCDs.

Hercules Computer Technology was one of the first 3rd party Graphics Card manufacturers for the IBM PC. It’s most popular product by-far was the original Hercules Graphics Card (HGC), which was widely cloned and supported by many applications and games. If an application or game list "Hercules" as an option, it is a reference to the original Hercules Graphics Card.

The PCjr was introduced by IBM in March 1984, and discontinued due to poor sales just over a year later. It’s integrated video card is backwards compatible with CGA, with the addition of a few modes:

The vertical refresh of the PCjr like CGA is 60Hz, which matches up well with the majority of modern 60Hz LCDs.

This mode can be set as follows in your DOSBox-X config file:

Video memory is fixed to 128KiB and cannot be changed.

In addition, DOSBox-X also has a few PCjr variants.

Equivalent to an early model IBM CGA connected to a composite monitor:

Equivalent to a late model IBM CGA connected to a composite monitor:

Tandy graphics, sometimes abbreviated to TGA, was introduced with the Tandy 1000 in 1984, which began as a clone of the IBM PCjr.

It has all the CGA and PCjr video modes, but some differences exist, such as how the video memory is mapped, which can cause incompatibilities. Later Tandy 1000 models added a video mode, called "Tandy Video II" or ETGA for 640x200 at 16 colours.

Tandy computers with Tandy Graphics were available on the market for much longer than the IBM PCjr, resulting in many games that supported it. Tandy computers were also made available with faster processors, up to a 286 running at 10MHz, while the original IBM PCjr was only ever available with a 4.77MHz 8088.

The vertical refresh of the Tandy 1000 like CGA is 60Hz, which matches up well with the majority of modern 60Hz LCDs.

This mode can be set as follows in your DOSBox-X config file:

Video memory is fixed to 128KiB and cannot be changed.

EGA stands for Enhanced Graphics Adapter and was introduced by IBM in 1984, as the official follow-on to CGA. It still only supports up to 16 colours on-screen, but out of a pallet of 64 colours and at a higher resolution.

This mode can be set as follows in your DOSBox-X config file:

The original IBM EGA came with just 64KiB video RAM, but could be upgraded to 128 or 256KiB.

The EGA emulation provided by DOSBox-X by default provides 256KiB of video RAM, by setting vmemsizekb= in the [video]section of the DOSBox-X config file, it is possible to reduce it instead to 64 or 128KB. e.g.,

One feature that was dropped with the introduction of EGA, was the composite output support. As such, EGA does not support CGA artefact colours.

The vertical refresh of EGA like CGA is 60Hz, which matches up well with the majority of modern 60Hz LCDs.

Amstrad in 1986 introduced the PC1512 which is an IBM PC clone with CGA (RGBI only) graphics, but also adds a 640x200 16-colour mode.

Very little software exists that can use this mode. Here are some known examples:

In addition, there is a PC1512.DRV driver for Sierra SCI0 and SCI1 games.

The vertical refresh of the Amstrad like CGA is 60Hz, which matches up well with the majority of modern 60Hz LCDs.

This mode can be set as follows in your DOSBox-X config file:

Video memory is fixed to 64KiB and cannot be changed.

The NEC PC-9800, simply known as the PC-98, were a family of computers made by NEC and sold in Japan throughout 1982 to 2000, which used MS-DOS with modifications to support the PC-98 BIOS and Japanese DBCS (Double Byte Character Set) characters. It’s supported in DOSBox-X by setting machine=pc98 in your DOSBox-X config file. More information about PC-98 support can be found in the PC-98 guide page:

JEGA is a variation of EGA for the Japanese market, conceived by Microsoft Japan and released in 1987 as part of AX (Architecture eXtended).

Its intended purpose was the display of the Japanese characters which required a higher resolution, as such this added a 640x480 video mode.

It was not very successful, as IBM introduced VGA shortly after which has a similar video mode.

The vertical refresh of JEGA like EGA and CGA is 60Hz, which matches up well with the majority of modern 60Hz LCDs.

This mode can be set as follows in your DOSBox-X config file:

Video memory is fixed to 256KiB.

DCGA is the video mode used by the Olivetti M24, AT&T 6300 and Toshiba T3100. DOSBox-X emulates the DCGA mode via the VGA mode.

This mode can be enabled by typing DCGA at the DOSBox-X prompt when you’re in a VGA video mode.

If you enable Toshiba J-3100 emulation (by setting dosv=jp and j3100=on in your DOSBox-X config file), then the J-3100 mode will be enabled when DOSBox-X starts. Typing the VGA command you can go to the Japanese DOS/V mode, and then typing DCGA command will return you to the J-3100 emulation mode.

MCGA stands for Multi-Color Graphics Array and was introduced by on April 2, 1987 as integrated in the IBM PS/2 Model 30 and a bit later that year on the Model 25. It features 64 KiB video RAM, and cannot be changed. No stand-alone MCGA cards were ever produced.

MCGA supports all CGA display modes (RGBI only) plus 640×480 monochrome at a refresh rate of 60 Hz, and 320×200 with 256 colours (out of a palette of 262,144) at 70 Hz. It does not however provide backwards compatibility with EGA. In effect, MCGA can be thought of as either an enhanced CGA card, or a cost-reduced VGA card.

As the high-colour mode is near identical to the one offered by VGA, many games have a combined "MCGA/VGA" video option, and selecting MCGA with a VGA adapter normally also works.

One rare example of a game that offers an MCGA option, but does not work on VGA is Thexder. This is not because the game could not have worked on VGA, but rather because it looks for specific machine settings that are only true on the above PS/2 Models. As such as part of the MCGA emulation, DOSBox-X also emulates some PS/2 specific machine settings, just enough to make games like Thexder work in MCGA mode.

This mode can be set as follows in your DOSBox-X config file:

Video memory is fixed to 64KiB and cannot be changed.

VGA stands for Video Graphics Array and was introduced by IBM in 1987. One of the stand-out features was that it could display up to 256 colours from a palette of 262,144. It features 256 KiB of video RAM (fixed), and is backward compatible with CGA (RGBI only), EGA and MCGA.

VGA adds the following new graphics modes:

One new feature is the ability to run at 70Hz vertical refresh, where CGA and EGA had only supported 60Hz. This is important for modern LCDs, as many will only run at 60Hz, which causes issues with many games that were designed to run at 70Hz, resulting in dropped frames. This can cause both video and audio distortion, as in many games the audio is linked to the frame rate.

Many clones were produced of the VGA adapter, often with more memory allowing higher colour depths, resolutions and refresh rates, in addition to various types of acceleration which were typically referred to as SuperVGA, or SVGA.

During the late 80’s and early 90’s many video card manufacturers existed, and as IBM was no longer leading the market, each manufacturer was doing its own thing in regard to setting their cards SVGA modes. Even different video chips from the same manufacturer were not necessarily compatible with each other.

This made it very difficult for software developers as they needed to support a plethora of different cards if they wanted to offer more than basic VGA.

As such the Video Electronics Standards Association (VESA) was born, and one of the first standardization efforts they led was the VESA BIOS Extensions (VBE).

The only emulated cards supported by DOSBox-X to provide VBE support are the S3 models, which all default to VBE 2.0.

There are many VESA settings available in the [video] section of the DOSBox-x config file, which are documented below.

links:

VGA Memory I/O delay in nanoseconds. Set to -1 to use default, 0 to disable.

Enable this option (-1 or nonzero) if you are running a game or demo that needs slower VGA memory (like that of older ISA hardware) to work properly. If your game is not sensitive to VGA RAM I/O speed, then turning on this option will do nothing but cause a significant drop in frame rate which is probably not what you want.

Amount of video memory in megabytes for the emulated SVGA adapter.

The maximum resolution and color depth the emulated SVGA adapter will be able to display is determined by this value.

For build engine games, use more memory than in the list above, so it can use triple buffering and thus won’t flicker.

Amount of video memory in kilobytes, in addition to that specified with vmemsize.

This setting is only supported by the emulated EGA and SVGA video adapters.

Controls VESA BIOS non-linear framebuffer window granularity in KB. This affects ONLY the VESA BIOS extensions.

Set 0 to functional normally.

Controls VESA BIOS non-linear framebuffer window size in KB. This affects ONLY the VESA BIOS extensions.

Set 0 to functional normally.

If set, allow VESA BIOS calls in IBM PC mode to set DAC width. Has no effect in PC-98 mode.

Set to false if you want to see high-intensity background colors instead of blinking foreground text. This option has no effect in PC-98 and some other video modes.

If non-zero, define the physical memory address in hexadecimal of the linear framebuffer.

Determines if the emulated SVGA adapter is PCI based.

This affects how the attribute controller maps colors, especially in 256-color mode.

Some SVGA cards handle the attribute controller palette differently than most SVGA cards.

If true, load a VGA BIOS from a ROM image file. If false, provide our own INT 10h emulation as normal.

If set, load the VGA BIOS from the specified file (must be between 1KB to 64KB in size).

If left unset, and DOSBox-X is asked to load a VGA BIOS from a file, a file name is chosen automatically based on the machine type. For example, Tseng ET4000 emulation (machine=svga_et4000) will look for et4000.bin.

VGA BIOS ROM images can be dumped from real hardware or downloaded from the PCem or 86Box ROMs collection.

Default ROM filenames:

VGA BIOS size override. Override the size of the VGA BIOS (normally 32KB in compatible or 12KB in non-compatible).

If true, save 4KB of EGA/VGA ROM space by pointing to the copy in the ROM BIOS of the first 128 chars.

Determines if a 14-pixel high font is available in the video BIOS ROM.

Determines if a 16-pixel high font is available in the video BIOS ROM.

If true, and emulating CGA/PCjr/Tandy, automatically provide the second half of the 8x8 ROM font.

This setting is ignored for EGA/VGA emulation. If false, you will need a utility like GRAFTABL.COM to load the second half of the ROM font for graphics.

Force the VGA framerate (refresh rate) to a specific value (ntsc, pal, or specific hz), no matter what. * ntsc = As used in North America is 60Hz * pal = As used in Europe and many other places is 50Hz

VGA specific resolutions normally default to 70Hz, although many clone VGA and SVGA cards supported higher values.

Whether to emulate a Sierra or compatible RAMDAC at IO port 3C6h-3C9h.

Some DOS games expect to access IO port 3C6h to enable highcolor/truecolor SVGA modes on older chipsets. Disable if you wish to emulate SVGA hardware that lacks a RAMDAC or (depending on the chipset) does not emulate a RAMDAC that is accessible through IO port 3C6h.

This option has no effect for non-VGA video hardware.

When emulating High Sierra highcolor RAMDAC, assume 5:6:5 at all times if set. Else, bit 6 of the DAC command selects between 5:5:5 and 5:6:5.

Set this option for demos or games that got the command byte wrong (MFX Transgrassion 2) or any other demo that is not rendering highcolor 16bpp correctly.

If true, DOSBox-X will fill inactive video memory regions with RAM rather than mapping them as empty.

This allows the ETen Chinese DOS system (e.g. ET16V and ET24VA) to run.

VGA debugging switch.

If true, an inverse line will be drawn on the exact scanline that the CRTC display offset registers were written.

This can be used to help diagnose whether the DOS game is page flipping properly according to vertical retrace if the display on-screen is flickering.

VGA debugging switch.

If true, an inverse green dotted line will be drawn on the exact scanline that the CRTC status port (0x3DA) was read.

This can be used to help diagnose whether the DOS game is properly waiting for vertical retrace.

IBM CGA in 80x25 text mode, when directly accessing the video memory during screen drawing, suffered from a distortion referred to as CGA "snow". This effect is not visible when the software uses the BIOS to write to the screen.

This only applies when machine=cga. Later video cards were not effected by this, nor were some clone CGA cards.

VGA status IO port 3BA/3DAh only defines bits 0 and 3. This setting allows you to assign a bit pattern in hexadecimal to the undefined bits.

The purpose of this hack is to deal with demos that read and handle IO port 3DAh in ways that might crash if all are zero.

If true, similar to the mainline DOSBox compatible BIOS mapping, a legacy 8x8 CGA font (first 128 characters) is stored at 0xF000:0xFA6E.

DOS programs that do not use INT 10h to locate fonts might require that the font is located there.

If true, similar to the mainline DOSBox compatible BIOS mapping, DOSBox-X will emulate the video parameter table and assign that to INT 1Dh. If false, the table will not be provided.

This option only affects EGA, VGA and SVGA emulation.

This option is needed for some older DOS applications that do some additional checks before detecting EGA/VGA hardware (SuperCalc).

If true, INT 10h will unmask IRQ 0 (timer) when setting video modes.

If set, bank switch (windowed) VESA BIOS modes will ignore the window selection when asked to bank switch. Requests to control either Window A or Window B will succeed. This is needed for some demoscene productions with SVGA support that assume Window B is available, without which graphics do not render properly. If clear, Window B is presented as not available and attempts to use it will fail. Only Window A will be available, which is also DOSBox SVN behaviour.

Controls whether calls to bank switch (set the window number) through the VESA BIOS apply range checking. If set, out of range window numbers will return with an error code. This is also DOSBox SVN behaviour. If clear, out of range window numbers are silently truncated to a number within range of available video memory and allowed to succeed. This is needed for some demoscene productions that rely on the silent truncation to render correctly without which drawing errors occur (e.g. end credits of Pill by Opiate)

This setting affects VESA BIOS function INT 10h AX=4F00h. If set, the VESA BIOS will zero the 256-byte buffer defined by the standard at ES:DI, then fill in the structure. If clear, only the structure members will be filled in, and memory outside the initial 20-32 bytes will remain unmodified.

Some very early 1990s DOS games that support VESA BIOS standards may need this setting turned OFF if the programmer did not provide enough space for the entire 256 byte structure and the game crashes if it detects VESA BIOS extensions

Needed for: GETSADAM.EXE

Whether to wait for vertical retrace if VESA Set Display Address is used to pan the display.

This affects only subfunction 0x00. Subfunction 0x80 will always wait as specified in the VESA BIOS standard.

It is recommended to set this to 1 for VBETEST.EXE so that the panning test and information does not go by too fast.

If non-zero, the VESA BIOS will report the linear framebuffer offset by this many scanlines. This does not affect the linear framebuffer’s location. It only affects the linear framebuffer location reported by the VESA BIOS. Set to nonzero for DOS games with sloppy VESA graphics pointer management.

MFX "Melvindale" (1996): Set this option to 2 to centre the picture properly.

If set, VESA BIOS SVGA modes will be set to map 128KB of video memory to A0000-BFFFF instead of 64KB at A0000-AFFFF. This does not affect the SVGA window size or granularity.

Some games or demoscene productions assume that they can render into the next SVGA window/bank by writing to video memory beyond the current SVGA window address and will not appear correctly without this option.

If true, EGA emulation allows changing horizontal pel (panning) register per scanline.

This is reportedly the behavior of IBM EGA hardware according to DOSBox SVN and enabled by default.

If false, EGA emulation latches hpel on vertical retrace end (like VGA does), which may have been EGA clone behavior that some games were written against.

Commander Keen episodes 4-6 need this option set to false when machine=ega.

This option affects only EGA emulation. To change VGA hpel behavior, use the allow hpel effects setting instead.

If true, allow the DOS demo or program to change the horizontal pel (panning) register per scanline. Some early DOS demos use this to create waving or sinus effects on the picture.

Not very many VGA chipsets allow this, so far, only ATI chipsets are known to support this effect.

If true, allow the DOS demo or program to make the picture wavy by playing with the 'start horizontal retrace' register of the CRTC during the active picture.

Some early DOS demos (Copper by Surprise!productions) need this option set for some demo effects to work.

If emulating hretrace effects, this parameter adds 'weight' to the offset to smooth it out.

The larger the number, the more averaging is applied. This is intended to emulate the inertia of the electron beam in a CRT monitor

If non-zero, the VESA modelist is capped so that it contains no more than the specified number of video modes.

If non-zero, VESA modes with horizontal resolution higher than the specified pixel count will not be listed.

This is another way the modelist can be capped for DOS applications that have trouble with long modelists.

If non-zero, VESA modes with vertical resolution higher than the specified pixel count will not be listed.

This is another way the modelist can be capped for DOS applications that have trouble with long modelists.

If true, the VESA modelist is placed in the VESA information structure itself when the DOS application queries information on the VESA BIOS.

Setting this option may help with some games, though it limits the mode list reported to the DOS application.

Some DOS games and demos assume one bit depth or the other and do not enumerate VESA BIOS modes, which is why this option exists.

If true, allow low resolution VESA modes (320x200x16/24/32bpp and so on).

You could set this too false to simulate SVGA hardware with a BIOS that does not support the low resolution modes for testing purposes, or to limit the amount of modes available.

If set, additional 24bpp modes are listed in the modelist regardless whether modes 0x100-0x11F are configured to be 24bpp or 32bpp. Setting this option can provide the best testing and development environment for new retro DOS code.

If set, offer HD video (16:9 aspect ratio) modes in the VESA modelist (such as 1280x720 aka 720p or 1920x1080 aka 1080p).

This option also offers 4:3 versions (960x720 and 1440x1080) for DOS games that cannot properly handle a 16:9 aspect ratio, and several other HD modes. The modes enabled by this option are still limited by the width and height limits and available video memory.

This is unusual for VESA BIOSes to do and is therefore disabled by default.

If true, unusual (uncommon) modes are added to the VESA modelist.

The modes reflect uncommon resolutions added by external drivers (UNIVBE), some VESA BIOSes, some laptop and netbook displays, and some added by DOSBox-X for additional fun.

If the DOS game or demo has problems with 32bpp VESA modes, set to 'false'.

These modes have the same 16-color planar memory layout as standard VGA, but at SVGA resolution.

If the DOS game or demo has problems with 24bpp (aka True Color) VESA modes, set to 'false'.

These modes have the same 16-color planar memory layout as standard VGA, but at SVGA resolution.

If the DOS game or demo has problems with 16bpp (aka High Color) VESA modes, set to 'false'.

These modes have the same 16-color planar memory layout as standard VGA, but at SVGA resolution.

If the DOS game or demo has problems with 15bpp VESA modes, set to 'false'.

These modes have the same 16-color planar memory layout as standard VGA, but at SVGA resolution.

If the DOS game or demo has problems with 8bpp (256 color) VESA modes, set to 'false'.

These modes have the same 16-color planar memory layout as standard VGA, but at SVGA resolution.

If the DOS game or demo has problems with 4bpp (16 color) VESA modes, set to 'false'.

These modes have the same 16-color planar memory layout as standard VGA, but at SVGA resolution.

If the DOS game or demo has problems with 4bpp (16 color) packed VESA modes, set to 'false'.

4bpp (16-color) packed is an unusual novelty mode only seen on specific Chips & Tech 65550 VESA BIOSes such as the one in a Toshiba Libretto laptop.

If the DOS game or demo has problems with VESA text modes, set to 'false'

This setting affects the VGA Line Compare register.

DOSBox-X can handle active display properly if games or demos reprogram vertical blanking to end in the active picture area. If the wraparound handling prevents the game from displaying properly, set this to false.

Out of bounds vblank values will be ignored.

Some DOS applications use VGA 256-color mode but accidentally clear the extended memory bit originally defined to indicate whether EGA hardware has more than 64KB of RAM.

Setting this option can correct for that. Needed for Mr. Blobby.

If the DOS game you are running relies on certain VGA raster tricks that affect active display area, enable this option.

This adds a delay between VGA mode changes and window updates. It also means that if you are capturing a demo or game, that your capture will also show a few garbled frames at any point mode changes occur, which is why this option is disabled by default.

If you intend to run certain DOS games and demos like DoWhackaDo, enable this option.

If true, changes to the Display End register of the CRTC do not trigger DOSBox-X to resize its window IF the value written is less than the current value.

Some demos like DoWhackaDo need this option set because of the way its raster effects work. If the DOSBox-X window rapidly changes size during a demo try setting this option. Else, leave it turned off.

Changes to other VGA CRTC registers will trigger a DOSBox-X mode change as normal regardless of this setting.

Update the VGA palette only on setting all 3 bytes.

Some demoscene productions use VGA Mode X but accidentally enable odd/even mode.

Setting this option can correct for that and render the demo properly.

This option forces VGA emulation to ignore odd/even mode except in text and CGA modes.

Synchronize vsync timing to the host display. Requires calibration within DOSBox-X.

Vsync rate used if vsync is enabled. Ignored if vsyncmode is set to host (win32).