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# Sega Genesis/MegaDrive Documentation

Last updated August 26, 2013
Valid as of 0.9.30.1

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. 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, heavily-modified 68K emulation core from Yabause, and Z80 emulation core from FUSE.

Sega Genesis/Megadrive emulation should still be considered experimental; there are still likely subtle 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.port1 | enum | none gamepad2 gamepad gamepad6 megamouse | gamepad | Input device for 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 Port 2 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 | xsmall small medium large | small | Disassembly font size. Note: Setting the font size to larger than the default may cause text overlap in the debugger. xsmall - 4x5 small - 5x7 medium - 6x13 large - 9x18
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.pixshader | enum | none autoip autoipsharper scale2x sabr ipsharper ipxnoty ipynotx ipxnotysharper ipynotxsharper | none | Enable specified OpenGL pixel shader. Obviously, this will only work with the OpenGL "video.driver" setting, and only on cards and OpenGL implementations that support pixel shaders, otherwise you will get a black screen, or Mednafen may display an error message when starting up. Bilinear interpolation is disabled with pixel shaders, and any interpolation, if present, will be noted in the description of each pixel shader. Note: Mednafen's pixel shaders do not work properly on some AMD graphics cards(there is a diagonal line of distortion) for an unknown reason, possibly a hardware bug. 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".
md.scanlines | integer | 0 through 100 | 0 | Enable scanlines with specified opacity. Opacity is specified in %; IE a value of "100" will give entirely black scanlines.
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, at high resolutions(such as 1280x1024; nn2x(or nny2x) + bilinear interpolation + fullscreen stretching at this resolution looks quite nice). 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 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 settings to have any effect, the ".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 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 settings to have any effect, the ".stretch" setting must be set to "0".