SHRIEK -- lets you change pitch and duration of the beep.

Usage:

insert this command near the end of your autoexec.bat file:

SHRIEK
or
SHRIEK duration frequency

e.g.  SHRIEK 250 554
      where duration is measured in milliseconds and frequency in Hertz.

Don't use SHRIEK more than once till you reboot.  Otherwise you
will end up with multiple copies of SHRIEK in RAM chained to
each other.  This will slow down screen paints.

What Is Shriek For
******************

Shriek changes the pitch or duration of the standard system
beep.  When you accelerate your XT or AT clone, sometimes the
ROM BIOS is not prepared for this eventuality.  Beep tones may
start coming out as piercing high-pitched shrieks.  Beep tones
may be too short in duration.  Shriek is a 96-byte TSR that
repairs this defect in your BIOS.  You can configure Shriek for
whatever pitch and duration you like best.

GETTING THE LATEST VERSION
**************************

Look for the latest version at my Web site:
  http://mindprod.com

How Does Shriek Work
********************

Shriek is a tiny 96 byte TSR than intercepts the Video INT 10
BIOS interrupt and handles making beep tones properly, while
allowing the normal BIOS routines to handle screen painting
functions.

How Shriek Makes a Tone
***********************

We set the countdown value for the hardware square wave generator
built in to the machine.  The hardware counts down, then pushes
the loudspeaker out.  Then it counts down again and then pushes
the loudspeaker in.  If it does this whole cycle 440 times a
second, you will hear middle A.

Unlike more primitive machines such as the Apple ][, once the
tone is started, the hardware can continue generating the sound
indefinitely without further help from the CPU.  When it is time
to turn off the tone, the CPU must then intervene to shut the
tone off.

Tone versus Frequency
*********************

       middle A ÄÄ¿    Frequency in Hz
 A =  55 110 220 440  880 1760 3520  7040 14080  = A
A# =  58 117 233 466  932 1865 3729  7459 14917  = B flat
 B =  62 123 247 494  988 1976 3951  7902 15804  = B
 C =  65 131 262 523 1047 2093 4186  8372 16744  = C
C# =  69 139 277 554 1109 2217 4434  8870 17740  = D flat   T
 D =  73 147 294 587 1175 2349 4699  9397 18795  = D        o
D# =  78 156 311 622 1245 2489 4978  9956 19912  = E flat   n
 E =  82 165 330 659 1319 2637 5274 10548 21096  = E        e
 F =  87 175 349 698 1397 2794 5588 11175 22351  = F
F# =  92 185 370 740 1480 2960 5920 11840 23680  = G flat
 G =  98 196 392 784 1568 3136 6272 12544 25088  = G
G# = 104 208 415 831 1661 3322 6645 13290 26580  = A flat

Roedy Green
Canadian Mind Products
#101 - 2536 Wark Street
Victoria, BC Canada V8T 4G8
tel:(250) 361-9093
mailto:roedyg@mindprod.com
http://mindprod.com

GETTING THE LATEST VERSION

Look for the latest version at my Web site:
  http://mindprod.com

It would also be helpful if you mentioned the URL or source of where
you got your copy.  I want to make sure that site is kept kept up to
date.

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