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Path: utzoo!watmath!clyde!floyd!harpo!seismo!hao!hplabs!sdcrdcf!randvax!jim
From: jim@randvax.ARPA (Jim Gillogly)
Newsgroups: net.micro.pc
Subject: Re: How to make PC beeps - Again
Message-ID: <1726@randvax.ARPA>
Date: Tue, 28-Feb-84 11:31:03 EST
Article-I.D.: randvax.1726
Posted: Tue Feb 28 11:31:03 1984
Date-Received: Sat, 3-Mar-84 23:05:30 EST
References: <2567@azure.UUCP>
Organization: Rand Corp., Santa Monica
Lines: 35

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There's a beep routine in the ROM at location E666.  It produces a beep
at 896 Hz (by my computations) (as opposed to the 1000 Hz that the
comments claim).  It reads as follows:

BEEP    PROC    NEAR
	MOV     AL,10110110B    ;SEL TIM 2,LSB,MSB,BINARY
	OUT     TIMER+3,AL      ;WRITE THE TIMER MODE REG
	MOV     AX,533H         ;DIVISOR FOR 896 HZ
	OUT     TIMER+2,AL      ;WRITE TIMER 2 CNT - LSB
	MOV     AL,AH
	OUT     TIMER+2,AL      ;WRITE TIMER 2 CNT - MSB
	IN      AL,PORT_B       ;GET CURRENT SETTING OF PORT
	MOV     AH,AL           ;SAVE THAT SETTING1