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Gens/GS: Sega Games Are Back With The Best Emulator

Last update: Oct 2, 2020

Gens/GS: Sega Games Emulator

So, what’s Gens/GS? It continued the legacy of Gens. During the 2000s, the best emulator was Gens, known as the Genesis emulator. Upon quitting Gens, its developers shared the codes for free. Consequently, this led to new versions of Gens. You may access about 10 versions stemming from the original ones.

Since they’re spin-offs, the way they function seems similar and thus, this article will help figure out how to install and start playing your retro games that were once your popular ones. Sonic Hedgehog or Altered Beast? No matter which game you pick, you may simply start playing on your computer right now.

How to install

As it’s a separate program, Gens/GS doesn’t come with an install wizard. Yet, the process is quite easy to do. You need to extract the file from compression. If you don’t know how to do that, you may watch the video showing it.

Note: It’s critical to put the Gens/GS file in a common folder of your computer. A good option may be putting it in Downloads, Documents, or just make a new folder on the desktop on your computer. If a Gens/GS file is located in your C drive which is the main one, then this means to restrict your file. You’ll make this file with read-only access.

After you locate your Gens/GS, it’s time to start the installation. All you do is double click on gens.exe.

How to set up the gamepad and keyboard

  1. Go to Options > Joypads:
  2. After that, you’ll see the following:
    see the following
  3. Configure Player 1 section is where you see keys and buttons associated with it. What you see is just default settings, and if this suits, no need to change the settings. Yet, if you plan to change something, read on the following.
  4. Before you start setting up your configurations on your keyboard or gamepad, you need to decide on the controller types. They come in 2 versions. As you may know, Genesis used to offer 2 types of gamepads, one with 3 buttons and the other with 6 buttons. To understand better, look at the picture below::
  5. The default settings are already set up according to the 6-button gamepad. You may shift to a 3-button one by choosing your option on the dropdown near the Port 1, as illustrated below:
    dropdown near the Port 1
  6. If a keyboard isn’t your favorite, plug in the gamepad you plan to use. If Gens/GS is open at that moment, close the program, and open it again.
  7. To shift a particular button, choose the “Change” which will serve the button’s function on your gamepad, which is illustrated below::
    Control config
  8. Press your keyboard or gamepad button you’re planning to set up for the virtual Genesis controller. You’ll go through all buttons automatically. All this is under Port 1.
  9. You successfully set up your Player 1 controller configurations. If you plan to add the second player, then all your configurations are to be done under Port 2. So, go to the same place and pass through the same procedures.

How to load a game

Note: if you’re planning to load your game from the Sega CD game, you need to skip to the section dedicated to Sega CD.

Many emulators have their specific folder of ROMS, a place of games. Yet, when it comes to Gens/GS, this isn’t a case. When you download your ROM, you can keep it anywhere, be it inside the Gens/GS folder or somewhere outside it. There’s no specific location requirement, but remember where you keep your ROMS.

So, how to load your game?

  1. Go to File menu, as shown below.
    Go to File menu
  2. You’ll see an Open ROM option, Ctrl+O. From here, you need to go to the place where your ROMs are kept. Select your game and click on Open.
    Open ROM
  3. The game will start automatically.

How to switch to Fullscreen?

Find Graphics > Full Screen. Yet, there’s a more straightforward way of doing it. Just press Alt+Enter. To leave Fullscreen, you may press Esc or Alt+Ent. When playing your game, you may easily access the menu if you click right on your mouse on the screen.

Problems with Fullscreen mode

The most ironic fact about this emulator is that there’s been no substantial update of Gens/GS despite being a trendy one. Thus, it’s not surprising to come across problems related to shifting to Fullscreen if you’re on Windows 8 or 10.

Yet, Windows has its solution to this glitch. It’s a feature known as Windows compatibility, enabling smooth playing with Fullscreen mode imitating Windows’s older versions. Check how you do that:

  • Click right with your mouse in your program, gens.exe, and left-click on Properties.
  • Select the Compatibility tab.
  • Here things get complicated, as every video card is specific and it’s hard to come up with one standard approach. However, you can do one of the following tips.
  • First, you may begin with selecting Run compatibility troubleshooter. All you need here is to follow the wizard. ‘Try recommended settings’ option should be tested at the beginning. If it doesn’t help, you better choose the ‘Troubleshoot program.’
  • Another way is to try running the emulator in compatibility mode under Windows 8 or older versions. For this, you need to choose ‘Run this program compatibility mode for.’ Here, you may select older versions where Gens/GS will work better..
    Run this program compatibility mode
  • Also, don’t forget about one annoying glitch that may happen when you set up Gens/GS to run under older Windows versions. Every time you open your emulator, you can be prompted with the following: ‘Do you want to allow the following program from an unknown publisher to make changes to this computer?’ The good news is that you need just to accept and that’s all.

Note: If crashing after fullscreen mode persists, the problem may be in the invalid video setting. You need to delete the gens.cfg file in the Gens/GS folder.

Using Screen filters

What are these filters for? They make the graphics better, and to access the screen filter list, you need to go to Graphics > Render, as indicated:

Choose one filter from the list, and the program will render the screen. But what about filters? You’ll find the following info useful in terms of choosing your filter:

Using Screen filters

Choose one filter from the list, and the program will render the screen. But what about filters? You’ll find the following info useful in terms of choosing your filter:

  • 2xSal, SuperSal: unite pixels by slightly blurring/aliasing them.
    2xSal, SuperSal
  • Blargg NTSC: nice filter imitating TV.
    Blargg NTSC
  • EPX, EPX Plus: unite pixels without a need for blurring/aliasing.
    EPX, EPX Plus
  • hq2x, hq3x, hq4x: pixel-rounder like EPX, but does it much better.
    hq2x, hq3x, hq4x
  • Scanline, Interpolated Scanline: add a horizontal line and thus simulating TV.
  • Scale2x, Scale3x, Scale4x: perform the same function as EPX.
    Scale2x, Scale3x, Scale4x

Saving your game

There’s a useful feature known as Save states. They save your game right at that moment whenever you decide. To save your game, you need to go to the File menu. Don’t forget this feature works correctly only with 32X and Genesis.

Saving your game

One important thing to keep in mind is that there are 2 types of save states. One is quick saves, and the other one is regular ones.

Quick save states

Here you may capture a quick save which is done with a shortcut of F5. Or you may go to File > Quick Save, and you’ve saved your game. To load your saved game with a quick load is also simple with a shortcut of F8. Or go to File > Quick Load.

Your F5 and F8 will help you with quick saves and loads. Yet, don’t forget that you’re given only 10 slots for various quick saves, from 0 to 9. The ‘0’ slot comes the first one. You may also shift the slots and for this, you go to File > Change State. Also, shortcuts like F6 for backward or F7 for forward will help you.

Regular save states

There’s also a standard but not so convenient method of saving your games. It has its explanations:

  • If you go to File > Save State As, you just enter a custom name. Let’s say you’re playing Street Rage, and you save the beginning of every stage, and therefore, filenames will be like Stage1, 2, etc.
  • It may happen that when you’re to save the file, the extension won’t show. You may have to enter the extension by yourself like ‘.gso,’ and all your saved files will be shown on your computer when loading them. One trick is that if you don’t want to enter the extension, just choose all files when loading, and you’ll find your saved game.
  • What’s so interesting about loading when you go to Files > Load State is that you may load games from different emulators, such as from Kega Fusion. Here, you simply may load your saved games even from other versions of Gens/GS on another computer.

How to take screenshots

To save your screenshots, you need to go to Graphics > Screenshot or just press Shift+Backspace. This will save your image in PNG format in the Gens/GS folder.

How to use Game Genie & Pro Action Replay

Game Genie

  1. At first, you load the game. Then go to Plugins > Game Genie.
  2. There’s a Code field where you’ll put the code you may find online. Be attentive when pasting the code so that there will be no spaces.
  3. In the field of Name, you’ll type a short description for the code.
  4. Then press the Add Code to add your code.
  5. Repeat this several times to have more codes added. Don’t forget that Gens/GS won’t support game cheats with multiple lines. Codes are to be added in one line and order. After you press OK, adding is complete.
  6. Restart your game. Then check whether your cheat works or not. If it doesn’t, it means you’ve entered the code incorrectly or it’s just a bad code.

Note: it’s not tricky to find cheats, and one of the primary sources is gamegenie.com. Also, you may search for the codes online. To do it efficiently, you should type the name of your game along with the game genie. For example, landstalker game genie.

Feature of fast forward

As the name suggests, you can speed up your game. Most emulators have one fast forward button with an adjusted speed. Unlike those emulators, Gens/GS allows you to adjust your speed on your own.

In total, you have 9 units of speed. You can increase or decrease. To make faster, you just need to press F4, and to reduce the speed, you need F3. Also, if you press F2, you turn your game into normal speed.

How to find ROMs

Finding your favorite games isn’t a challenging task at all. There are many places where you may get these ROMs, and all you need is to write, as an example, download castlevania bloodlines.

Transfer of saved games to another emulator

Is it possible to transfer the save states to another emulator? Yes, it’s possible if this another emulator is Kega Fusion. Yet, this won’t work if you transfer your saved games to other Genesis emulators.

The good news is that if you transfer your saved games to other Gens/GS emulators, this won’t be difficult. You may share your saved files with other gamers if they’re using your emulator. Or just save your games and go on with them on other computers.

What if this emulator doesn’t save games?

If you’re new to emulators like Gens/GS and still trying to find out all nuances, you may have the following issues:

  • Your saved states don’t work properly, and when you save your games and try to load them, nothing appears.
  • When saving RPG at a particular point of the game, you may be surprised to find out that your saved game is lost.
  • Also, you may have problems with configurations that haven’t been saved, and this means you have to reconfigure everything.

The solution to the following issues is an obvious one. The root of the problem is the location of your emulator. It’s just located in a read-only place, so you need to replace Gens/GS to a common location like Downloads, Documents, etc.

About Sega CD

The Sega CD emulator works a bit differently, and there are some details to know about it.

Downloading Sega CD ISO

The games of this emulator were available with audio CDs. The data on CDs were broken into two parts. The first part used to belong to game data, and the other part was dedicated to the games’ soundtrack.

Ripping Sega CD games has been similar, as was in CDs. So, game data and soundtracks have led to different formats to download. These games are generally found in the BIN file format for game data, audio tracks, and a CUE sheet. The last one is the text of the programmatic list of tracks. Given the complexity of these games, you can download 4 types of ISOs, as described below:

  1. Binary BIN/CUE: the most recent versions for Sega CD, and when you get the files, they look as shown in the picture:
    Binary BIN/CUE
  2. All the files shown above are in BIN format, and if to look at the CUE sheet, you’ll see that these BIN files will look like below:
  3. Standard BIN/CUE: it’s like all conventionally ripped CDs and saved as ISO files. Thus, when you open the files, they’ll look like the following:
    Standard BIN/CUE
  4. ISO/MP3: in the 2000s and 2010s, such formats were quite popular, given the Internet wasn’t fast as it’s now. Audio tracks were converted to MP3 files, which reduced the size of Sega CD ROMs. So, you get the following:
  5. The good news is that this format is compatible with both Gens/GS and Kega Fusion. Yet, they’re not supported on other emulators.
  6. ISO/WAV: you get this when ISO/MP3 is converted to WAV, making it playable on any Genesis emulators with Sega CD support.

Note: all the above-mentioned formats are also known as Sega CD ISO.

A different way to save

For Gens/GS, saving your Sega CD game will be different from the real one. The real Sega CD system includes internal memory the capacity of which isn’t that great and external RAM carts.

Gens/CD gives every game both internal memory and external cart. Yet, all this gives an advantage of more space as well. However, with internal memory and an external RAM cart, you’ll have to format the game’s memory if you plan to play a new one.

For games where saving is quite significant, as in RPG games, the game may not let you proceed until you format the memory. Perhaps, it sounds a bit complicated, but the process of formatting is easy to perform.

Making copies on the real one

If you download Sega CD, you may easily burn to CD-R and play on the real stuff. There are no copyright things to worry about. At the end of this article, you’ll find the info on how you may burn ISO to CD-R.


If you want to boot Sega CD games, you have to download the Sega CD BIOS. Every region has its particular one. You can download them online.

How to set up the BIOS

How to set up the BIOS

  1. After downloading, you need to extract the BIOS from its compressed version and put it in the same folder where Gens/GS is located.
  2. Go to Options > BIOS/Misc Files.
  3. Now, you look below SegaCD BIOS Files, and there are BIOS fields. Press the Change button you see inside the red circle for your BIOS you want to set. Find the location of your BIOS file, pick it, and press on Save. Then, press on OK upon completion.

How to load Sega CD games

Following this article, you should’ve read about Sega CD emulation, and:

  1. Understand ISO formats.
  2. Know how differently Sega CD saves if to compare with the real one.
  3. Have downloaded and already set up Sega CD BIOS.

It’s time to start loading Sega CD games on your emulator.


  1. If you’ve downloaded your game in ROM format, it’s okay. Yet, sometimes people download the file in compressed formats like 7Z or RAR. Here, you’ll need a separate program to install so that you can unzip the game in ROM format.
  2. This program for unzipping is free of charge and easily downloadable. After downloading this program, it’s time to unzip your ROM by 7-Zip > Extract here, as illustrated below:
    Sega CD ISO
  3. If your file is in ISO/MP3 or BIN/CUE, pay attention to whether there’s a CUE sheet. It happens that they may not be included. Without this sheet, your program won’t work. Look at the CUE sheet:
    ISO/MP3 or BIN/CUE
  4. If you’ve found that this sheet is missing, don’t panic. There’s an app called Sega CUE Maker that generates CUE sheets.
  5. Open the CUE in Notepad and pay attention to the image below:
    Open the CUE in Notepad

You need to check the following:

  • First of all, check if the ISO name matches the actual ISO file’s name. Be sure the names match.
  • Check if the names of the audio track match the real audio files.
  • Another important aspect is whether the format of the audio tracks matches. If your files are in MP3 format, it means that the CUE should show MP3 files, not other formats. Yet, if you happen to discover that your CUE has WAV files, whereas the real files are in MP3 format, you better do a Find/Replace on the Notepad. With this, you’ll change all of them to MP3.
  • Time to load the Sega CD ISO. Find File > Load SegaCD Image. If your game has been downloaded as an ISO/MP3 or BIN/CUE, you have to click on the CUE. But, to load a game in a single ISO file, you simply click on the ISO file and get your game.
  • What you see now is the Sega CD BIOS screen, demonstrated below. All you need to do is to press the START button.

Sega CD BIOS screen

Note: If you see the CD player screen but not the game when you press the START button, it means you have a problem related to your game file. Perhaps, the game is invalid. You need to revise the steps described above to see if everything is done properly. And if that doesn’t work out, you have to download your game from a different source.

How to load a real Sega CD game or CD-R copy

Loading games from the CD-ROM drive isn’t always advisable. Such means of loading games can entail problems and, as expected, slowing of the game itself. Instead, the better approach will be to rip the CD to a BIN/CLUE format file.

As this format won’t take up much space on your HDD, ripping your CD games is the best option. Moreover, it’ll be a digital backup of your game as CDs aren’t good when it comes to quality and can be easily lost.

Loading your Sega CD game or CD-R copy

Note: If your computer works under older Windows (XP, 98, ME) and you have problems with Gens/GS detecting CD drive, your solution might be installing ForceASPI.

  1. Insert your game CD into CD-ROM. Now, you’ll have to wait, as it can take some time depending on the computer. Close the Windows pop-up saying, ‘What do you want to do with this CD?’
  2. Then, you find File > Boot CD. Here, you need to wait for the game to load.
  3. What you see now is the Sega CD BIOS screen, demonstrated below. All you need to do is press the START button.

START button

Note: If you see the CD player screen but not the game when you press the START button, it means you have a problem related to your game file. Perhaps, the game is invalid. The problem can be with your CD-R copy, caused by a bad burn. And if that doesn’t work out, you have to download your game from a different source.

Once your game has started functioning, you better read the following 2 sections on Perfect Sync and formatting the memory.

About Perfect Sync

Why do you need this feature of Perfect Sync? This feature enables your Gens/GS emulator to send less commands while emulating the Sega CD game. For games, this feature should be enabled; otherwise, some game points may lock up from the very start.

Let’s say you’re playing ‘Popful Mail,’ and it won’t boost past its logo. You need to activate this feature to go further. It’s not clear why the emulator doesn’t automatically turn this on, yet to do it on your own becomes inevitable.

How to activate this feature:

  1. Go to CPU > SegaCD Perfect Sync (SLOW).
  2. If the game is on, just close it and restart. Then, load your game.

Note: Always remove the check on Perfect Sync after playing your game. Since not all games require this option, this will cause problems with gaming.

How to format the memory

This isn’t always required. Yet, when playing RPGs and some other games, you may face the issue saying ‘Backup RAM not initialized.’ Then, it means you have to format the memory.

format the memory

  1. When you’re at the BIOS screen, you need to press B, a button you set up before starting your gaming.
  2. Then, you’ll be redirected to the CD player screen which you see above. Here, you need to press OPTION.
  3. You’ll see a different screen showing some information regarding the memory. Just move on.
  4. Now, you continue with the screen above to manage the Sega CD game’s memory. Initially, you need to format the internal memory, which you can do by pressing the following:
  5. Here, you’re to select Yes to complete formatting internal memory.
  6. Then, you have to format external memory, RAM cart, and you go to the following:
    RAM cart
  7. Again here, you select Yes to complete the format.
  8. That’s it and now select Exit.
  9. After you come back to the CD Player screen, select CD-ROM to boot the CD.

Changing CDs

Have you heard of such games as Night Trap or Ground Zero Texas? What do they have in common? They come in two CDs. When it’s time to change them, you’ll see a CD tray icon. It’s at the bottom left corner.

When you see the CD tray’s flash at the corner, it signals for swapping CDs. It means to load the second CD ISO. That’s all you need to do.

How to remove Sega CD LEDs

remove Sega CD

The Sega CD emulator has 2 indicators in the form of light blinking. The first one is a green light. It means that something is READY for use, and the other one is red, meaning to need for ACCESS. These lights are located at the bottom left.

Of course, the lights aren’t in the middle or very visible place. Yet, their blinking can be a bit disturbing. Removing these lights isn’t something challenging, so just follow the instructions:

  1. Find Options > General Options.
  2. Uncheck the Show SegaCD LEDs.

What to do in case of ‘Backup ROM not initialized’ error?

All you need is to format the memory. With this article, you may learn how to do that instantly.

Freezing issue at the start of the game

The solution, as was explained above, is activating Perfect Sync. Don’t forget, not all games require this feature to be on.

Problem with playing music

Remember the important aspect of CUE sheets. You need to verify the CUE sheets and that everything is done properly.

Blank loading screen along with audio index error

When loading a Gens/GS game, you may get a black screen accompanied by an unusual audio index message at the top.

Blank loading screen

The reasons aren’t clear, though. This might be a case when you load the CUE. The solution is simple, and you need to load ISO or BIN rather than the CUE sheet.

How to burn Sega CD games from ISO files

The following is intended for burning BIN/CUE or ISO/MP3 archives to a CD. As you already know, there’s no copyright stuff on the Sega CD system. You may simply play copies without any problems.

Don’t forget about CUE

Before you start burning the process, be sure you have a CUE sheet. If there’s no CUE, the process will be done in vain. When you don't have it, generate it with Sega CUE Maker.

MP3 to WAV

If the game you downloaded comes in ISO/MP3 format, you’ll have to convert the MP3 files to WAV. The best option to do so is with a free program of WinLAME. It’s easy to find and download this program. To convert the MP3 files into WAV, you need to do the following:

  1. Run WinLAME. Press the button Open, find the MP3 location folder, choose all of them, and press Open. On the white box, you get the list of the files you have chosen. Now, select Next to move on.
  2. You reach the ‘Output Settings,’ and under ‘Output Module,’ you should select Wave Output. Look at the following:
    Run WinLAME
  3. Press Next and move on the next part.
  4. In the next section of ‘Presets,’ everything is set as default and no need to change anything, so select Next to move on.
  5. Now, you’re at the section of ‘Encoding,’ and just click the Play button to start the conversion process.

How to edit the CUE

If the game is in ISO/MP3 format, you’ll have to edit the sheet as you get new WAV tracks from the conversion with WinLAME. It’ll look like this:

edit the CUE

‘Find what’ will find you MP3, and ‘Replace with’ will change it to WAV.

How to burn to CD

After the completion of the previous steps, it’s time to burn your game to CD-R. You can use either CD-RW or CD-R discs.

  1. Firstly, you need to download and install the ImgBurn program available for free on its homepage.
  2. When you open ImgBurn, just press Write image file to disc, as indicated below:
    burn to CD
  3. Below the ‘Source,’ press the folder icon, which you see below:
    Below the Source
  4. Find the location of your Sega CD ISO, and then, choose the CUE sheet and select Open, illustrated below:
    Find the location of your Sega CD ISO
  5. Have a look at the following image:
    look at the following image
  6. Insert your disc, and when you do it, you’ll get the info no 1 indicated above. Then, be sure your CD is chosen, generally done automatically.
  7. Press the icon to start burning. Much depends on your CD-drive. The process will take up to several minutes to be completed. If you’re done, it’s time to get started playing your games.

Note: It happens that after burning, there might be problems with playing music. It means you did something wrong. Look through the directions above and find where you made a mistake.

How to copy and back up Sega CD games

These directions will help you copy a Sega CD game or CD-R copy.

  1. Firstly, you need to download and install the ImgBurn program available for free on its homepage.
    install the ImgBurn program
  2. Don’t forget to get an ISO file from your Sega CD game. Open ImgBurn and then press Create image file from disc, as you can see from the image above.
  3. Don’t forget to indicate the right source drive, set in Source. After that, press on Read.
    press on Read
  4. To get an ISO file from your game, the ripping process may take about half an hour or even less. After the process is complete, the program automatically will place the ripped file into the Documents. In case of BIN/CUE of the game, you just follow the same directions above. And that’s all.

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