Category : Assembly Language Source Code
Archive   : ZENASM.ZIP
Filename : LST3-1.ASM

;
; *** Listing 3-1 ***
;
; Times speed of memory access to Enhanced Graphics
; Adapter graphics mode display memory at A000:0000.
;
mov ax,0010h
int 10h ;select hi-res EGA graphics
; mode 10 hex (AH=0 selects
; BIOS set mode function,
; with AL=mode to select)
;
mov ax,0a000h
mov ds,ax
mov es,ax ;move to & from same segment
sub si,si ;move to & from same offset
mov di,si
mov cx,800h ;move 2K words
cld
call ZTimerOn
rep movsw ;simply read each of the first
; 2K words of the destination segment,
; writing each byte immediately back
; to the same address. No memory
; locations are actually altered; this
; is just to measure memory access
; times
call ZTimerOff
;
mov ax,0003h
int 10h ;return to text mode