source: xtideuniversalbios/trunk/Assembly_Library/Src/TimerTest.asm@ 421

; Project name  :   Assembly Library
; Description   :   Tests for Assembly Library.

;
; XTIDE Universal BIOS and Associated Tools 
; Copyright (C) 2009-2010 by Tomi Tilli, 2011-2012 by XTIDE Universal BIOS Team.
;
; This program is free software; you can redistribute it and/or modify
; it under the terms of the GNU General Public License as published by
; the Free Software Foundation; either version 2 of the License, or
; (at your option) any later version.
; 
; This program is distributed in the hope that it will be useful,
; but WITHOUT ANY WARRANTY; without even the implied warranty of
; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
; GNU General Public License for more details.      
; Visit http://www.gnu.org/licenses/old-licenses/gpl-2.0.html
;       

; Include .inc files
%define INCLUDE_DISPLAY_LIBRARY
%define INCLUDE_TIME_LIBRARY
%include "AssemblyLibrary.inc"  ; Assembly Library. Must be included first!


; Section containing code
SECTION .text

; Program first instruction.
CPU 486
ORG 100h                        ; Code starts at offset 100h (DOS .COM)
Start:
    jmp     BusMeasurements_Start

; Include library sources
%include "AssemblyLibrary.asm"

%macro MOV_TIMING_LOOP 1
    xor     bx, bx                  ; Offset for memory transfers
    mov     dx, OFFSET_TO_NEXT_WORD ; Must be at least 32 (Pentium Cache Line size)
    wbinvd                          ; Flush and invalidate internal cache
    cli                             ; Disable interrupts
    START_PRECISE_EVENT_TIMER
ALIGN 8
%%ReadNextWord:
    mov     ax, %1                  ; 2 bytes
    add     bx, dx                  ; 2 bytes
    jnc     SHORT %%ReadNextWord    ; 2 bytes
    STOP_PRECISE_EVENT_TIMER
    sti
%endmacro


;--------------------------------------------------------------------
; Program start
;--------------------------------------------------------------------
ALIGN JUMP_ALIGN
BusMeasurements_Start:
    CALL_DISPLAY_LIBRARY InitializeDisplayContext
    xor     ax, ax
    mov     ds, ax

    call    MeasureRegAndMemMovDurationDifferenceToAX
    call    GetBusCycleTimeToAXfromRegAndMemMovDurationDifferenceInAX
    call    GetBusClockRateFromCycleTimeInAX
    mov     si, g_szBusMeasurements
    call    PrintBusMeasurements

    call    AssumeVlbCycleTimeToAXfromBusCycleTimeInCX
    call    GetBusClockRateFromCycleTimeInAX
    mov     si, g_szVlbAssumption
    call    PrintBusMeasurements

    ; Exit to DOS
    mov     ax, 4C00h           ; Exit to DOS
    int     21h



;--------------------------------------------------------------------
; MeasureRegAndMemMovDurationDifferenceToAX
;   Parameters:
;       DS:     Segment for memory read tests
;   Returns:
;       AX:     Difference in register and memory access durations
;               (Precise Event Timer Ticks)
;   Corrupts registers:
;       BX, CX, DX
;--------------------------------------------------------------------
MeasureRegAndMemMovDurationDifferenceToAX:
    call    SystemTimer_IntializePreciseEventTimer

    MOV_TIMING_LOOP bx
    call    SystemTimer_GetPreciseEventTimerTicksToAX
    xchg    cx, ax      ; Duration now in CX

    MOV_TIMING_LOOP [bx]
    call    SystemTimer_GetPreciseEventTimerTicksToAX
    sub     ax, cx      ; AX = Difference in durations
    sub     ax, cx
    ret


;--------------------------------------------------------------------
; We must divide the duration by 4 since the timing loop loads
; whole cache line (4 times the bus width) instead of single BYTE.
;
; GetBusCycleTimeToAXfromRegAndMemMovDurationDifferenceInAX
;   Parameters:
;       AX:     Difference in register and memory access durations
;               (Precise Event Timer Ticks) 
;   Returns:
;       AX:     Duration for single BYTE in nanosecs
;   Corrupts registers:
;       CX, DX
;--------------------------------------------------------------------
GetBusCycleTimeToAXfromRegAndMemMovDurationDifferenceInAX:
    mov     dx, TIMER_CYCLE_TIME
    mul     dx          ; DX:AX = Duration in nanosecs
    mov     cx, (65536 / OFFSET_TO_NEXT_WORD) * 4
    div     cx          ; AX = Duration for single BYTE in nanosecs
    ret


;--------------------------------------------------------------------
; GetBusClockRateFromCycleTimeInAX
;   Parameters:
;       AX:     Bus Cycle Time in nanosecs
;   Returns:
;       CX:     Bus Cycle Time in nanosecs
;       DX:     Bus Clock Rate (MHz)
;       AX:     Clock Rate tenths
;   Corrupts registers:
;       Nothing
;--------------------------------------------------------------------
GetBusClockRateFromCycleTimeInAX:
    xchg    cx, ax
    xor     dx, dx
    mov     ax, 1000
    div     cl          ; AL = MHz, AH = Remainder
    xchg    al, dl      ; DX = Bus Clock Rate, AL = 0
    aad                 ; AX = 10 * AH (+AL)
    div     cl
    xor     ah, ah      ; AX = Tenths
    ret


;--------------------------------------------------------------------
; AssumeVlbCycleTimeToAXfromBusCycleTimeInCX
;   Parameters:
;       CX:     Bus Cycle Time in nanosecs
;   Returns:
;       AX:     Assumed VLB Cycle Time in nanosecs
;   Corrupts registers:
;       Nothing
;--------------------------------------------------------------------
AssumeVlbCycleTimeToAXfromBusCycleTimeInCX:
    mov     ax, cx
    cmp     al, 24      ; 25 = 40 MHz
    jb      SHORT .AssumePentiumSoDivideBy2
    ret
.AssumePentiumSoDivideBy2:
    shr     ax, 1
    ret


;--------------------------------------------------------------------
; PrintBusMeasurements
;   Parameters:
;       CX:     Bus Cycle Time in nanosecs
;       DX:     Bus Clock Rate (MHz)
;       AX:     Clock Rate tenths
;       SI:     Offset to string to format
;   Returns:
;       Nothing
;   Corrupts registers:
;       AX, DX, BP
;--------------------------------------------------------------------
PrintBusMeasurements:
    mov     bp, sp
    push    cx
    push    dx
    push    ax
    CALL_DISPLAY_LIBRARY FormatNullTerminatedStringFromCSSI
    ret



; Section containing initialized data
SECTION .data

OFFSET_TO_NEXT_WORD     EQU 32  ; Must be at least 32 (Pentium Cache Line size)

g_szBusMeasurements:
    db  "Detected bus cycle time of %u ns (%u.%u MHz) ",LF,CR,NULL
g_szVlbAssumption:
    db  "Assuming VLB (if exists) cycle time of %u ns (%u.%u MHz) ",LF,CR,NULL
g_szDashForZero:        db      "- ",NULL



; Section containing uninitialized data
SECTION .bss