API?
API means Application Programmers Interface. An API makes it easier for a programmer to create an application. When using an API, standard commands can be used which means there is no need to re-invented the wheel each time. Also, an API makes it easier to write programs that are compatible across different platforms. As a Voodoo user, there are three different API's that you should know about:

- DirectX

- Glide

- OpenGL

DirectX7 compatibility with Voodoo3 drivers 1.02.18 and below
The 1.02.18 and lower drivers are not fully DirectX7 compatible. Some system experience trouble while using these drivers and DirectX7. Use DirectX 6.1 with these drivers. The speed improvement gained by DirectX7 versus DirectX6.1 are little to none. Uninstalling DirectX7 is not easy, so I wouldn't recommend trying DirectX7 to see if it works on your system.
If you already have DirectX7 installed and you are not experiencing any problems combined with the 1.02.18 or lower drivers, you will not have to uninstall it. If you are experiencing trouble don't forget to check the "Direct 3D troubles" section. It might be one of the general D3D troubles instead of DirectX7 specific.
The oldest drivers that do support DirectX7 are the 1.03 drivers, which where distributed in two seperate driver kits for DirectX 6 and DirectX 7. Most users had no problem using the 1.02.11 drivers with DirectX 7.

DirectX7 not working with 1.03 drivers
Make sure you have downloaded the correct version of the 1.03 drivers. There is a DirectX 6.1 and a DirectX7 version of these drivers.

Uninstalling DirectX7
DirectX 7 is an integral part of Windows 95/98 now and cannot be uninstalled.
That's what Microsoft says about this. But you might want to try dxun, the DirectX Uninstaller by ebrink. You will have to use the 1.1 patch to uninstall DirectX7.
Another way to uninstall DirectX 7 is to use SETUP /ND. The switch /ND makes setup ignore new files & overwrite the files with what is on the Windows 98 disk. You will have to redownload all updates.

If your Glide and OpenGL games work fine, but Direct 3D games always give you a blank screen when you try to run them

- Previous Voodoo owners upgrading

This is directly from the "Voodoo Banshee FAQ" located at the 3dfx website:

Question #3

I had a Voodoo Graphics or Voodoo2 that I replaced with a Voodoo Banshee board. Now I cannot run any games, all I get is an error message or a black screen. Voodoo Graphics and Voodoo2 install a registry key that is used by Direct3D to build a list of secondary devices. If you remove a Voodoo Graphics and Voodoo2 card but do not uninstall the drivers this registry key remains. Games will continue to try and use Voodoo Graphics or Voodoo2 but will fail as the hardware is not present. To fix the problem you should un-install your existing Voodoo card as specified by the manufacturer of your board. If no uninstall procedure is documented you can download the following .inf file that will remove the registry key Direct3D looks for. The delv. inf file will remove the Direct3D registry keys used by Voodoo Graphics and Voodoo2. To use: download the file (Question # 3 on the Banshee FAQ), using Windows Explorer right mouse button click on the file in the download location and choose "Install". If you use the delv.inf file you will no longer be able to access Voodoo Graphics or Voodoo2 as a Direct3D device. If you installed the delv.inf file by mistake and need to re-enable the Direct3D key for your Voodoo2 or Voodoo Graphics card follow these steps: Download the restore file for Voodoo Graphics or Voodoo2. Then using Windows Explorer right mouse button click on the file in the download location and choose "Install".

- If no previous Voodoo card has been installed in the system then there is a registry conflict with a previous display adapter and the registry entries for the previous display card will have to be removed. Please see the "Registry cleaning" section.

- If Direct3D games are crashing back to the desktop etc. and you have an AMD K6 Super Seven board then you will need to set up your BIOS properly. Please look at the "BIOS settings" section.

- Also read the stuttering info below

Stuttering/Chrashing with transparencies
There seems to be a bug in the Direct3D drivers in the Voodoo3 driver version 1.02.11 & 1.02.18. It seems when tranparencies (like smoke or glass) are displayed, the display stutters, missing frames. Some machines even seem to crash when transparencies are displayed. The oldest Voodoo3 drivers (v1.00.00) seem to solve the stuttering problem and are available from the VoodooFiles. If you are experiencing crashes in these games and tried installing the old drivers, please mail me to let me now if this solves it. Thanks!
Another solve someone mentioned was given to him by a Siemens Nixdorf engineer who suggested reverting to an older version of his bios. It solved his stuttering with his Gigabyte GA-5AX Super Socket 7 motherboard.

Direct3D games crashing
Make sure your motherboard is compatible with the V3. Check out the motherboard section

"No hardware acceleration found" when starting a Direct3D game
Click "Start: and "Run..." and type in "dxdiag"
Click on the "Display" tab at the top of the DirectX diags window. You should see a button that says "Test Direct3D" If that test works, then the problem is with the game.
If that doesn't work - make sure that Direct3D is enabled on that same window (there will be a button next to it that says "Enable" if it is disabled). If it says "no acceleration is available", close the dxdiag tool and go to the Control Panel - double click "System," then the Performance tab, then the "Graphics" button - and make sure the slider is on full "hardware acceleration", then reboot. You will now be able to enable the "Direct3D" acceleration in the dxdiag tool.

DxDiag doesn't show AGP detected on the display page
This is normal for a Voodoo card. Basically there are 3 kinds of AGP implementation as indicated in Intel's paper:

1. Uses the AGP just as a faster PCI slot. (for example Banshee and Voodoo3/4/5)

2. Uses the AGP with the local video card memory for buffers and system memory for textures. (for example Intel i740)

3. Uses the AGP with the local video card memory for buffers and texture and system memory for textures. (for example TNT, G400)

Some diagnostics and utilities fail to identify that the card is AGP if the card uses the first approach, like Final Reality for example. Do not worry about this.

Direct3D FSAA settings will not be saved
In some cases Direct3D FSAA settings will not be saved UNLESS you first set the OpenGL/Glide FSAA ON FIRST.

Why can't I use Alt-Tab to switch in and out of games?
You will need to make sure you are using the latest drivers for the Voodoo3 adapter. Games that are designed for Glide 2.X will not function with the Alt+Tab function since Glide 2.X does not support it.

Will there be any revisions made to the Glide with Voodoo4 and 5?
No revisions were necessary. V4 and V5 products are compatible with all existing Glide titles and will support Glide 2.x and 3.x.

NFS3 won't recognize my Voodoo3
There is a patch for NFS3 on the Voodoo3: http://www.ea.com/tech_support/patch_detail.cfm?id=15567

Klingon Honour Guard and other old (pre-Voodoo3) games
If you don't want to run this game in software mode try the following:

The solution is to (a) get the latest KHG patch and (b) get the banshee version of glide2.dll from the banshee drivers and stick it in the KHG\system directory. For some reason KHG works if it thinks your V3 is a banshee. The same goes for some other games out there. The latest glide2.dll in this driver kit "vbw9x-10300-dx7.exe" (latest directx7 banshee kit):

Voodoo Banshee(tm) Driver kit: 1.03.00
Voodoo Banshee Glide(tm) 2.X Driver: 2.61.00.0438

does NOT solve the problem.

but the release before (version number shown below) this does.

Voodoo Banshee(tm) Driver kit: 1.02.03
Voodoo Banshee Glide(tm) 2.X Driver: 2.60.00.0350

Enabling 3D Now! in Half Life by using the q2 3D Now! patch
Take out the file 3dfxglam from your q2 patch and copy it to your HalfLife\gldrv directory.
Go in the text file there and enter this line: 3dfxglam.dll 3dNOW/3Dfx MiniGL
The later is just the name you see in the video menu.

Why can't I use Alt-Tab to switch in and out of games?
From Jarrod at 3dfx Tech Support
I have tried to research this as thoroughly as possible. Using the new (V1.02.11 or V1.02.18) drivers, I have tested successfully alt-tabbing in the following games:

Quake II, V3.15 and V3.20
Quake III pre alpha build 1.08
Starsiege Tribes V1.00
Unreal Tournament Demo
NFS III

Other games will be tested as time (and getting a copy of the game) allows.
Here are some interesting notes about OpenGL alt-tabbing:
Using Quake II V3.15
Voodoo 3
V3 driver build V1.02.11
Video options set to "default OpenGL"
-alt-tab works
-ctrl-esc works
-alt-esc works
Change video options to "3dfx miniGL"
-alt-tab kills the game
The problem here is the miniGL. With the newest drivers you don't need it. The newest drivers have the full OpenGL ICD in them, and the "default OpenGL" looks better than the "3dfx miniGL" mode does.
This was also tested with Quake II V3.20 with the same results. It does work.
Use the new drivers: V1.02.11 or V1.02.18
Set the Video option to "default OpenGL"
If you still can't alt-tab then delete the Quake directory and reinstall it.

OpenGL applications other than games won't work
Basically, the Voodoo card is designed for games. The OpenGL ICD is too. Unfortunatly this means 3dfx will make sure all popular games (like Quake 1/2/3) will work, but won't go much beyond that. Make sure you try the latest drivers. If you still can't get a specific product to work, you might want to try old drivers. Old drivers can be downloaded from Voodoo.dk.

Improving performance
Use the OpenGL ICD, not the MiniGL with version 1.02.18 and above.

Trouble using OpenGL ICD
If you can't get the OpenGL ICD to work, try setting your desktop color depth to 16bit.
If you still can't get it to work, try the following: Go the start,find and open find file. Search for 3dfxogl.dll when it pops up copy and paste to desktop leaving the original in the windows/system folder. then rename it to 3dfxgl.dll then put it in any game folder that uses the 3dfx mini gl such as Half-life, Quake 2, and Sin. Then when you play the game instead of using the Minigl you will use the Full Opengl ICD. This will also work for GLquake, but you have to rename it to OpenGL32.dll instead of 3dfxgl.dll.

The date on my Opengl32.dll in my Win/Sys folder is 8/24/96
That's right. That's when Microsoft last updated their OpenGL32.dll file. It's dated correctly. For old Windows at least. Win98 (first release) OpenGL32.dll is dated 05/11/98, and W98SE might even have a newer date, the point is the 3dfxOGL.dll file is not going to replace the Microsoft file, it will be called upon when needed.

WickedGL
Lots of users have reported great visual and performance gains from using the WickedGL drivers instead of the original drivers. Give them a try! For K6-2/III systems the OpenGL ICD from 3dfx will often give better performance due to excellent 3D Now! support (The WickedGL drivers don't have any 3D Now! optimization).