Wednesday, May 28, 2014

Vintage PC Game Music - Supporting as Many Early Music Devices as Possible

Music in PC games existed before the 1990s.  First there was the PC Speaker, then PCjr. and Tandy 3-voice sound, next came expansion boards like the Adlib and Game Blaster and supported MIDI devices like the MT-32, and finally the Sound Blaster.  My goal is to combine as many of these devices as practical in a single system.  Since the PC Speaker is ubiquitous, the choice of systems seems unlimited.

Of the other devices, Tandy 3-voice sound first was supported in games in 1984 (PCjr.), and sound cards and MIDI devices first were supported in late 1988.  However, the need for Tandy 3-voice sound limits the system to a Tandy 1000, since that chip was never implemented in a compatible ISA card.  Additionally, only a Tandy with 8-bit slots and Tandy video should be considered, since modifying either gives real compatibility problems.

As I have previously indicated, the Tandy 1000 TL and the TX are the best candidates here.  The TL/2 and TL/3 are not as good choices because they have one fewer slot than the older machines.  That slot is better used by an ISA or SCSI interface that can interface to a hard drive.

The TL has a PSSJ sound chip which includes 8-bit digitized sound capabilities.  It can support up to a 44KHz sample output rate.  The Sound Blaster 1.0-1.5 only support a 23KHz sample output rate, but the 2.0 supports a 44KHz sample rate.  The PSSJ and the Sound Blasters work similarly and both use IRQ7 (selectable, but early games insist on 7) and DMA1 (cannot be changed or fully disabled) and tend to crash when the other is present.  They will not coexist happily in the same system, and there is nothing that can be done about it.

While the PSSJ may look better than the Sound Blaster for digital playback, there are two additional issues to consider.  First, early games with digitized sound are not going to playback samples at 44KHz because they take up so much disk space.  Even then, samples tend to be short, so any playback differences are not likely to be noticeable. More importantly, games using the Sound Blaster for digital playback will accept gameport input, games using the PSSJ will not during sample playback.  If there is a good deal of sample playback, like in Outrun and Prince of Persia, the joystick will not work at all.

The TX doesn't have the PSSJ, therefore the Sound Blaster is the sound card with the best digitized support from early games.  The Sound Blaster includes the Adlib chip and can easily include the Game Blaster chips for a few dollars.  However, the TX has a built-in gameports that cannot be disabled, so the Sound Blaster's gameport will have to be disabled.

On the TL, separate Adlib and Game Blaster boards will be required.  I am not so comfortable suggesting a Sound Blaster Pro because many games supporting Game Blaster will only write to I/O 220-223, and that is where the OPL2 chips are located on a Sound Blaster Pro.  Similarly, many early Sound Blaster games will only support the Sound Blaster at I/O 220-22F.  While a non-upgraded Sound Blaster will not cause trouble at I/O 220-223, it uses the rest of the I/O ports and the Game Blaster also uses those I/O ports for autodetection.

Additionally, an MPU-401 interface card will be required, few games support the Sound Blaster MIDI interfacer.  There is a driver to allow most Sierra games to work with the Sound Blaster MIDI interface. With the MPU-401, you can connect to the MT-32, the FB-01 and the Casio devices supported in Sierra and Accolade games.

Therefore, on the TL, three cards are devoted to sound, and on the TX there are two.  In my ideal system, one bay should be used for a 5.25" drive, and a second bay for a 3.5" drive.  A TL has an extra bay for a hard drive, and the TX may require a slot-CF adapter, otherwise a bay or a hard card will be required.

1 comment:

  1. i didn't buy reader rabbit but at the radio shack i could hear voice "this is reader rabbit" on the 1000tx!

    3-voice could do voice.

    were there any games that took advantage of the 1000tl superior sound?

    the sierra games i played worked fine with sx