It is an unfortunate fact of PC retro gaming that the Gravis Ultrasound cards are very expensive to buy off the second-hand market and the auction sites. You may ask why should I want one, my Sound Blaster and my Roland does the trick for me.
For most games, you would be correct, the GUS is not especially impressive. Some games, like anything using the DOOM engine, mix all the digital audio in software and then send the result to the sound card. This eliminates one of the most important advantages of the GUS, mixing multiple streams in hardware at reasonable bit-sizes and frequencies. In this instance, the GUS is no better than a Sound Blaster 16. In benchmarks, it is actually worse than a SB16.
But for other games, the GUS can have a distinct advantage. In these games, all audio, music, speech and sound effects, is digitally generated and mixed. The Sound Blasters must mix this audio in software, but the GUS mixes it in hardware. The result is always a higher quality sound from the GUS than an SB, even if the SB is a Pro, 16 or AWE model.
Here is a list of known games which take advantage of the GUS's hardware mixing :
Crusader: No Remorse
Crusader: No Regret
Jazz Jackrabbit (including CD-ROM and Holiday episodes)
The Lemmings Chronicles
One Must Fall 2097
Pinball Arcade (includes special versions of Pinball Dreams & Pinball Dreams 2)
Star Control II
I have decided to record a sample of the output from my GUS ACE and my SB Pro 1.0 from my 486DX2/66 computer. The settings I found to work the best with these games is SET ULTRASND=240,6,7,11,5. This sets the Base Address to 240, the playback DMA channel to 6, the recording DMA channel to 7, the GUS IRQ to 11 and the Sound Blaster/MIDI IRQ to 5. These are the settings to which the card is initialized with ULTRINIT when the system boots into DOS.
Some games will have skips or lag in the GUS playback if the ISA bus speed is set to the default, 8.25MHz, but setting it to 7.19MHz in the BIOS seems to eliminate most problems. Setting it to 6.6MHz is required for smooth playback in the DOOM games and One Must Fall 2097. Other people get their Utrasounds working fine without needing separate DMA and IRQ settings or lowering the bus speed. I do not know if this is an issue particular to the ACE or to the SiS motherboard chipset (SiS 85C471 + 85C407) I am using.
The first game here is Star Control II, which is one of the first games really to support the GUS. One of the most obvious benefits of the GUS over the SB is stereo support. SC2 only supports the basic Sound Blaster, it has no specific support for the Pro or the 16. Sometimes, SC2 on my computer with the music or a sound effect being played back by the GUS will hang, giving a very unpleasant machine-gun like noise. Disabling and reenabling the sound and music fixes the problem.
Next comes Epic Pinball, where the GUS shows a clear improvement over the SB Pro. For this game, I let the demo run from the title screen, which gives a demonstration of the Android table. There is support for stereo sound effects, namely the sound of the flippers, on both the GUS and the SB Pro. The ACE 1.0 has the stereo channels reversed compared to other GUS cards, so I used a pair of RCA to minijack cables to correct this issue. The SB Pro also has the stereo channels reversed, but the switched cable above fixes the issue.
Third in my list is One Must Fall 2097. This game sounds really rough on the Sound Blaster, as it was being recorded as broadcast through an AM radio station. Both Epic Pinball and One Must Fall were published by Epic MegaGames, but each were developed by third parties. They may share sound drivers, because both drivers have the same quality settings for the Sound Blaster options. I choose the High Quality (486DX/50) settings. The Maximum Quality settings suggests a Pentium and I wanted to give a 486-quality experience.
Finally, we have Pinball Fantasies. Pinball Fantasies has given me the least amount of trouble with the GUS for all the games. The quality difference between the GUS and the SB Pro is not quite as pronounced. Unlike Epic Pinball, there is no stereo sound effect for the flippers. Pinball Fantasies supports full digital audio through the PC Speaker and the Covox Speech Thing, whereas you only get typical PC speaker sound effects from Epic Pinball. I have added recordings for the PC Speaker and Covox, demonstrating the best you can get with some very crude hardware on a 486DX2/66.
In conclusion, despite all the wrestling and the setup you have to do with a GUS, I think most people would find the overall improvement in audio quality to be worth it. Of course, I haven't even mentioned the DOS demos. The GUS was the bedrock of the DOS demoscene, and if you have one you are good to go for just about any demo except really early demos like Crystal Dream and Copper. Not all DOS demos support the Sound Blaster, and many classic demos like Unreal and Second Reality that support both are not going to sound as good as they would with a GUS.