[Dx4win] Some more info concerning Compaq Presario.

[BielefeldJ@andovercontrols.com]

I have done some experiments with the SVGA signal lines concerning why certain monitors
may kill the sound system.

On the SVGA socket
 pin 11 = Sense 0
 pin 12 = Sense 1
 pin 4   = Sense 2
 pin 15 = Sense 3

The bit pattern of these sense bits indicate the type of monitor is being connected.

I found (for the Compaq Presario) that if pin 4 (Sense 2) is not shorted to ground the BIOS will shut 
off the volume control. This computer originally was packaged with a monitor with integrated
speakers and a volume control knob. The older monitors did not use the Sense bits and like my
older monitor pin 4 was omitted. I had to insert a small wire into pin 4 on the PC's SVGA socket
and run it to the socket's screw terminal to ground the pin. Now I can use an older monitor and
still have the volume control working.

I hope this will help some in the future with a weird Compaq product.

Regards,
John
K1JEB