Mednafen Sega Genesis/MegaDrive Documentation

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# Sega Genesis/MegaDrive Documentation

Last updated March 19, 2024
Valid as of 1.32.1

Table of Contents:

- Introduction
- Settings Reference

## Introduction

Mednafen's Sega Genesis/Megadrive emulation is based off of Genesis Plus and information and code from Genesis Plus GX(old GPL-licensed version). The GPL-incompatible CPU and sound emulation cores in the aforementioned projects have been replaced with GPLed or GPL-compatible alternatives; heavily-modified and improved YM2612 emulation from Gens, and Z80 emulation core from FUSE.

Sega Genesis/Megadrive emulation should still be considered experimental; there are still likely timing bugs in the 68K emulation code, the YM2612 emulation code is not particularly accurate, and the VDP code has timing-related issues.

Sega 32X and Sega CD are not currently supported, though there is a bit of stub Sega CD code present currently.

## Settings Reference

Caution: Any settings that change emulation behavior as seen from the emulated game are shown with the setting name bolded in the table. One should be conscious of these settings if one has changed them from the default values when using network play or movies, as they can cause desychronizations if not set the same among hosts(or between the recording emulator and the playing emulator).

Setting: | Value Type: | Possible Values: | Default Value: | Description:
--- | --- | --- | --- | ---
md.cdbios | string |  | us_scd1_9210.bin | Path to the CD BIOS SegaCD/MegaCD emulation is currently nonfunctional.
md.correct_aspect | boolean | 0 1 | 1 | Correct the aspect ratio.
md.input.auto | boolean | 0 1 | 1 | Automatically select appropriate input devices. Automatically select appropriate input devices, based on an internal database. Currently, only multitap device usage data is contained in the database.
md.input.mouse_sensitivity | real | through | 1.00 | Emulated mouse sensitivity.
md.input.multitap | enum | none tp1 tp2 tpd 4way | none | Enable multitap(s). none - No multitap(s). tp1 - Team Player/Sega Tap on MD/Genesis port 1. tp2 - Team Player/Sega Tap on MD/Genesis port 2. tpd - Team Player/Sega Tap on both MD/Genesis ports. 4way - EA 4-Way Play
md.input.port1 | enum | none gamepad2 gamepad gamepad6 megamouse | gamepad | Input device for Virtual Port 1 none - none gamepad2 - 2-Button Gamepad gamepad - 3-Button Gamepad gamepad6 - 6-Button Gamepad megamouse - Sega Mega Mouse
md.input.port2 | enum | none gamepad2 gamepad gamepad6 megamouse | gamepad | Input device for Virtual Port 2 none - none gamepad2 - 2-Button Gamepad gamepad - 3-Button Gamepad gamepad6 - 6-Button Gamepad megamouse - Sega Mega Mouse
md.input.port3 | enum | none gamepad2 gamepad gamepad6 megamouse | gamepad | Input device for Virtual Port 3 none - none gamepad2 - 2-Button Gamepad gamepad - 3-Button Gamepad gamepad6 - 6-Button Gamepad megamouse - Sega Mega Mouse
md.input.port4 | enum | none gamepad2 gamepad gamepad6 megamouse | gamepad | Input device for Virtual Port 4 none - none gamepad2 - 2-Button Gamepad gamepad - 3-Button Gamepad gamepad6 - 6-Button Gamepad megamouse - Sega Mega Mouse
md.input.port5 | enum | none gamepad2 gamepad gamepad6 megamouse | gamepad | Input device for Virtual Port 5 none - none gamepad2 - 2-Button Gamepad gamepad - 3-Button Gamepad gamepad6 - 6-Button Gamepad megamouse - Sega Mega Mouse
md.input.port6 | enum | none gamepad2 gamepad gamepad6 megamouse | gamepad | Input device for Virtual Port 6 none - none gamepad2 - 2-Button Gamepad gamepad - 3-Button Gamepad gamepad6 - 6-Button Gamepad megamouse - Sega Mega Mouse
md.input.port7 | enum | none gamepad2 gamepad gamepad6 megamouse | gamepad | Input device for Virtual Port 7 none - none gamepad2 - 2-Button Gamepad gamepad - 3-Button Gamepad gamepad6 - 6-Button Gamepad megamouse - Sega Mega Mouse
md.input.port8 | enum | none gamepad2 gamepad gamepad6 megamouse | gamepad | Input device for Virtual Port 8 none - none gamepad2 - 2-Button Gamepad gamepad - 3-Button Gamepad gamepad6 - 6-Button Gamepad megamouse - Sega Mega Mouse
md.region | enum | game overseas_ntsc overseas_pal domestic_ntsc domestic_pal | game | Emulate the specified region's Genesis/MegaDrive game - Match game's header. Emulate the region that the game indicates it expects to run in via data in the header(or in an internal database for a few games that may have bad header data). overseas_ntsc - Overseas(non-Japan), NTSC Region used in North America. overseas_pal - Overseas(non-Japan), PAL Region used in Europe. domestic_ntsc - Domestic(Japan), NTSC Region used in Japan. domestic_pal - Domestic(Japan), PAL Probably an invalid region, but available for testing purposes anyway.
md.reported_region | enum | same game overseas_ntsc overseas_pal domestic_ntsc domestic_pal | same | Region reported to the game. same - Match the region emulated. game - Match game's header. This option, in conjunction with the "md.region" setting, can be used to run all games at NTSC speeds, or all games at PAL speeds. overseas_ntsc - Overseas(non-Japan), NTSC Region used in North America. overseas_pal - Overseas(non-Japan), PAL Region used in Europe. domestic_ntsc - Domestic(Japan), NTSC Region used in Japan. domestic_pal - Domestic(Japan), PAL Probably an invalid region, but available for testing purposes anyway.

Setting: | Value Type: | Possible Values: | Default Value: | Description:
--- | --- | --- | --- | ---
md.debugger.disfontsize | enum | 5x7 6x9 6x12 6x13 9x18 | 5x7 | Disassembly font size. Note: Setting the font size to larger than the default may cause text overlap in the debugger. 5x7 - 5x7 6x9 - 6x9 6x12 - 6x12 6x13 - 6x13. CJK support. 9x18 - 9x18; CJK support.
md.debugger.memcharenc | string |  | shift_jis | Character encoding for the debugger's memory editor.
md.enable | boolean | 0 1 | 1 | Enable (automatic) usage of this module.
md.forcemono | boolean | 0 1 | 0 | Force monophonic sound output.
md.scanlines | integer | -100 through 100 | 0 | Enable scanlines with specified opacity. Opacity is specified in %; IE a value of "100" will give entirely black scanlines. Negative values are the same as positive values for non-interlaced video, but for interlaced video will cause the scanlines to be overlaid over the previous(if the "video.deinterlacer" setting is set to "weave", the default) field's lines.
md.shader | enum | none autoip autoipsharper scale2x sabr ipsharper ipxnoty ipynotx ipxnotysharper ipynotxsharper goat | none | Enable specified OpenGL shader. Obviously, this will only work with the OpenGL "video.driver" setting, and only on cards and OpenGL implementations that support shaders, otherwise you will get a black screen, or Mednafen may display an error message when starting up. When a shader is enabled, the "md.videoip" setting is ignored. none - None/Disabled autoip - Auto Interpolation Will automatically interpolate on each axis if the corresponding effective scaling factor is not an integer. autoipsharper - Sharper Auto Interpolation Same as "autoip", but when interpolation is done, it is done in a manner that will reduce blurriness if possible. scale2x - Scale2x sabr - SABR v3.0 GPU-intensive. ipsharper - Sharper bilinear interpolation. ipxnoty - Linear interpolation on X axis only. ipynotx - Linear interpolation on Y axis only. ipxnotysharper - Sharper version of "ipxnoty". ipynotxsharper - Sharper version of "ipynotx". goat - Simple approximation of a color TV CRT look. Intended for fullscreen modes with a vertical resolution of around 1000 to 1500 pixels. Doesn't simulate halation and electron beam energy distribution nuances.
md.shader.goat.fprog | boolean | 0 1 | 0 | Force interlaced video to be treated as progressive. When disabled, the default, the "video.deinterlacer" setting is effectively ignored with respect to what appears on the screen, unless it's set to "blend" or "blend_rg". When enabled, it may be prudent to disable the scanlines effect controlled by the "md.shader.goat.slen" setting, or else the scanline effect may look objectionable.
md.shader.goat.hdiv | real | -2.00 through 2.00 | 0.50 | Constant RGB horizontal divergence.
md.shader.goat.pat | enum | goatron borg slenderman | goatron | Mask pattern. goatron - Goatron Brightest. borg - Borg Darkest. slenderman - Slenderman Spookiest?
md.shader.goat.slen | boolean | 0 1 | 1 | Enable scanlines effect.
md.shader.goat.tp | real | 0.00 through 1.00 | 0.50 | Transparency of otherwise-opaque mask areas.
md.shader.goat.vdiv | real | -2.00 through 2.00 | 0.50 | Constant RGB vertical divergence.
md.special | enum | none hq2x hq3x hq4x scale2x scale3x scale4x 2xsai super2xsai supereagle nn2x nn3x nn4x nny2x nny3x nny4x | none | Enable specified special video scaler. The destination rectangle is NOT altered by this setting, so if you have xscale and yscale set to "2", and try to use a 3x scaling filter like hq3x, the image is not going to look that great. The nearest-neighbor scalers are intended for use with bilinear interpolation enabled, for a sharper image, though the "autoipsharper" shader may provide better results. none - None/Disabled hq2x - hq2x hq3x - hq3x hq4x - hq4x scale2x - scale2x scale3x - scale3x scale4x - scale4x 2xsai - 2xSaI super2xsai - Super 2xSaI supereagle - Super Eagle nn2x - Nearest-neighbor 2x nn3x - Nearest-neighbor 3x nn4x - Nearest-neighbor 4x nny2x - Nearest-neighbor 2x, y axis only nny3x - Nearest-neighbor 3x, y axis only nny4x - Nearest-neighbor 4x, y axis only
md.stretch | enum | 0 full aspect aspect_int aspect_mult2 | aspect_mult2 | Stretch to fill screen. 0 - Disabled full - Full Full-screen stretch, disregarding aspect ratio. aspect - Aspect Preserve Full-screen stretch as far as the aspect ratio(in this sense, the equivalent xscalefs == yscalefs) can be maintained. aspect_int - Aspect Preserve + Integer Scale Full-screen stretch, same as "aspect" except that the equivalent xscalefs and yscalefs are rounded down to the nearest integer. aspect_mult2 - Aspect Preserve + Integer Multiple-of-2 Scale Full-screen stretch, same as "aspect_int", but rounds down to the nearest multiple of 2.
md.tblur | boolean | 0 1 | 0 | Enable video temporal blur(50/50 previous/current frame by default).
md.tblur.accum | boolean | 0 1 | 0 | Accumulate color data rather than discarding it.
md.tblur.accum.amount | real | 0 through 100 | 50 | Blur amount in accumulation mode, specified in percentage of accumulation buffer to mix with the current frame.
md.videoip | enum | 0 1 x y | 1 | Enable (bi)linear interpolation. 0 - Disabled 1 - Bilinear x - Linear (X) Interpolation only on the X axis. y - Linear (Y) Interpolation only on the Y axis.
md.xres | integer | 0 through 65536 | 0 | Full-screen horizontal resolution. A value of "0" will cause the current desktop horizontal resolution to be used.
md.xscale | real | 0.01 through 256 | 3.000000 | Scaling factor for the X axis in windowed mode.
md.xscalefs | real | 0.01 through 256 | 1.000000 | Scaling factor for the X axis in fullscreen mode. For this setting to have any effect, the "md.stretch" setting must be set to "0".
md.yres | integer | 0 through 65536 | 0 | Full-screen vertical resolution. A value of "0" will cause the current desktop vertical resolution to be used.
md.yscale | real | 0.01 through 256 | 3.000000 | Scaling factor for the Y axis in windowed mode.
md.yscalefs | real | 0.01 through 256 | 1.000000 | Scaling factor for the Y axis in fullscreen mode. For this setting to have any effect, the "md.stretch" setting must be set to "0".