BLASTER Environment Variable

The BLASTER environment variable was used to allow applications to determine the settings in use for an installed Sound Blaster card when operating under MS-DOS.

BLASTER Variable

The format of the variable (set via AUTOEXEC.BAT usually) was,

SET BLASTER=A220 I5 D1 T3 P330 H6 E620
 |    |     |    |  |  |  |    |  |
 |    |     |    |  |  |  |    |  |_______ AWE 32 Only Parameter
 |    |     |    |  |  |  |    |__________ "High" DMA Channel
 |    |     |    |  |  |  |_______________ MIDI Port
 |    |     |    |  |  |__________________ Type of Card
 |    |     |    |  |_____________________ DMA Channel
 |    |     |    |________________________ Interrupt
 |    |     |_____________________________ Port Address
 |    |___________________________________ Environment Variable
 |________________________________________ DOS Command

NOTE: There can be no spaces between the word BLASTER and the equal sign (=). If you have a space in there, your system will read the parameter incorrectly, and it will not be recognised.

The P, H, and E parameters are dependant on certain types of cards (in particular, E is only needed with the AWE 32).

Minimum Configuration

The minimum requirements are to have the A, I, D, & T parameters. The other three may or may not be needed depending on what type of card you have. In particular, when using clone cards, or some card that's not a "true" Soundblaster, most likely only A, I, D, and T are needed.

Underlying Configuration

The variable settings must match the underlying settings on the card, which are either set by physical jumpers on the board, or (on later cards) via some PnP BIOS or configuration utility.

Port

For PORT ADDRESS, it's almost always 220. That seems to be the default for most sound cards out there, and unless you know you've switched it away from 220, it's a safe bet it's still there.

Interrupt

The INTERRUPT is something that varies from system to system. Mystic Towers and games prior to Raptor require that your IRQ be set at 7 or less. IRQ2 isn't recommended, as it's used for cascade to interupts 9..15 in AT class systems and hence causes problems.

The DMA CHANNEL sometimes causes problems if it isn't set to 1, which is the usual default. If it is not set correctly, software may lock up when sound is turned on.

Card Type

The TYPE OF CARD should be:

• 1 if you have an older Soundblaster, or a Sound Blaster emulating card
• 2 for an older Soundblaster Pro
• 3 if you have a newer plain Soundblaster
• 4 for a newer Soundblaster Pro

MIDI Port

The MIDI PORT parameter will only be needed if you are using a card that has MIDI capabilites. If so, this is where you define what MIDI port you are using. 330 seems to be the default, so if you have a MIDI card, and you haven't changed anything from factory defaults, this is probably where it still is.

High DMA Channel

The HIGH DMA CHANNEL is something that is used primarily on Soundblaster 16 cards. This is not the same as the standard DMA channel, this is a different one. This is only used if you're using a 16 bit sound card capable of playing 16 bit Soundblaster sounds. By default, this is usually 5, so unless you know that it's something else, it's probably still 5.

AWE Cards

The E620 parameter is needed only with the Creative Labs AWE 32 sound card. If you have one of these, this parameter will have been set up properly assuming you've installed the software that came with the card. Check your AWE 32 documentation for a more thorough explanation of what this parameter is used for.

Note on the Soundblaster AWE64: The AWE64 will not always correctly set up its sound drivers for use in Windows 95 in relation to DOS games.

See Also

• Sound Blaster