Category : Utilities for DOS and Windows Machines
Archive   : SLWDN.ZIP

Output of file : SLOWDOWN.ASM contained in archive : SLWDN.ZIP
title SLOWDOWN.COM System Slowdown Routine 86.04.05a.dkg
name dev
page 60,132
TUNE_SPEED equ 224 ; tune to your CPU speed (approx Mhz*28)
CR equ 0dH
LF equ 0aH
; |
; PURPOSE: Provide a method to run an 8MHz 8086 based machine |
; at a comparable speed to the IBM for stupid programs |
; that assume a certain processor speed in their timing. |
; |
; FUNCTION: Intercept the tick interrupt and run a time-waster |
; loop for a user-settable delay before returning to the |
; running program. |
; |
; TO USE: From DOS, type SLOWDOWN [] where is |
; percentage of the CPU wasted. |
; |
; WRITTEN: 85.07.26 by David K. Goodwin |
; MODIFIED: 86.04.05.dkg, added intvec removal code |
; |


; Program Segment Prefix

NUM_CHARS db ? ; number of characters in argument
db ? ; leading blank
ARGTX db ? ; start of text (after leading blank)
; Program Area
ORG 100H
begin: jmp start
db 'Copyright 1986, David K. Goodwin'
; Interrupt Service Routine
; This routine will perform a time-waster loop every system clock tick
; 18 times per second. All memory references must use the CS segment prefix
; because that is the only segment setup by the INT call. I am using a
; method of Intercept routine ID somewhat like that done in CPMPLUS RSX's
; to prevent any conflict of this routine with any others that might
; intercept the interrupt I am using.
intvec dd ? ; next interrupt routine in sequence
loopcnt db ? ; number of 1% loops
db 'SLOWDOWN' ; Interrupt Intercept ID
tickint: pushf ; save flags
push ax ; save our useful reg
mov ah,cs:loopcnt ; load our loop counter
tick1: push cx
tick2: loop tick2
pop cx
dec ah
jnz tick1
pop ax ; restore reg
popf ; restore flags
jmp cs:[intvec] ; go to next routine in chain

saveaddr label byte ; used as last location to keep in mem
; Start of main routine to process the command line.
mov dx,offset signon
mov ah,9
int 21H
mov bx,offset argtx ; point to start of text argument
mov cl,num_chars ; set cx to number of chars in argument
xor ch,ch ; "
sub cx,1 ; discount char count for leading blank
ja parse_arg ; if so, handle w/termination routine

error: mov dx,offset errmsg ; if a problem give user help
error2: mov ah,9
int 21h
mov ax,4c01h ; terminate
int 21h
; Parse the numeric argument
; If the number is greater than 99 then we will error out with usage.
; If argument is zero, we will "unload" the interrupt service routine.
parse_arg: mov al,0 ; initialize char value to 0
mov dh,10d ; digit multiplier
getdigit: mov dl,[bx] ; get char code into dl
sub dl,'0' ; convert digit code to value
jb error ; error checks
cmp dl,'9' ;
ja error ; must be a digit
mul dh ; mult. char value (in al) by 10
add al,dl ; add digit value to char value
inc bx ; skip to next char
dec cx ; "
jnz getdigit ; exit if at end of text (cx = 0)
cmp al,99 ; if over 99, error
ja error
mov loopcnt,al ; save our loop counter
mov ah,35h ; get old tick interrupt
mov al,1ch
int 21h
sub bx,8 ; check for interrupt already alive
mov ax,word ptr es:[bx] ; get first 2 chars
cmp ax,'LS' ; if SL, already exists
je exists ; do mod of routine
cmp loopcnt,0 ; if zero, jump to removal routine
jnz chgint
mov dx,offset notresmsg
jmp error2
chgint: add bx,8 ; get intvec back to normal
mov word ptr intvec,bx
mov word ptr intvec+2,es
mov ah,25h ; save new int vector
mov al,1ch
mov dx,offset tickint
int 21h

; Done with loading and initialize
; Print out a message to say we did it and leave
complete: mov dx,offset byemsg ; point to completion message
mov ah,9 ; code for dos display string function
int 21h ; display message via dos function call
mov ah,31h ; keep program in memory for int vector
mov al,0
mov dx,offset saveaddr
int 21h ; bye bye
notresmsg: db 'SLOWDOWN not resident$'
byemsg: db 'SLOWDOWN loaded$'

exists: mov al,loopcnt ; get specified loopcnt
cmp al,0 ; if we are removing
jz rmvint
dec bx ; point int copy of loopcnt
mov byte ptr es:[bx],al ; save percentile
mov dx,offset existmsg
jmp goodret
existmsg: db 'SLOWDOWN started at new value$'

rmvint: sub bx,5 ; point to old intvec
push ds
lds dx,es:[bx] ; get old int vector
mov ah,25h ; restore old int vector
mov al,1ch
int 21h
pop ds
mov dx,offset rmvmsg
jmp goodret
rmvmsg: db 'SLOWDOWN removed$'

goodret: mov ah,9
int 21h
mov ax,4c00h ; terminate
int 21h

signon: db 'SLOWDOWN v1.1a 86.04.05.dkg',CR,LF,'$'
errmsg: db CR,LF
db 'usage: a>SLOWDOWN ',CR,LF
db ' where is between 0 and 99',CR,LF
db ' if is 0, remove slowdown interrupt',CR,LF
db '$'

code ends

end begin

  3 Responses to “Category : Utilities for DOS and Windows Machines
Archive   : SLWDN.ZIP

  1. Very nice! Thank you for this wonderful archive. I wonder why I found it only now. Long live the BBS file archives!

  2. This is so awesome! 😀 I’d be cool if you could download an entire archive of this at once, though.

  3. But one thing that puzzles me is the “mtswslnkmcjklsdlsbdmMICROSOFT” string. There is an article about it here. It is definitely worth a read: