+++ /dev/null
-;\r
-; *** Listing 2-5 ***\r
-;\r
-; The long-period Zen timer. (LZTIMER.ASM)\r
-; Uses the 8253 timer and the BIOS time-of-day count to time the\r
-; performance of code that takes less than an hour to execute.\r
-; Because interrupts are left on (in order to allow the timer\r
-; interrupt to be recognized), this is less accurate than the\r
-; precision Zen timer, so it is best used only to time code that takes\r
-; more than about 54 milliseconds to execute (code that the precision\r
-; Zen timer reports overflow on). Resolution is limited by the\r
-; occurrence of timer interrupts.\r
-;\r
-; By Michael Abrash 4/26/89\r
-;\r
-; Externally callable routines:\r
-;\r
-; ZTimerOn: Saves the BIOS time of day count and starts the\r
-; long-period Zen timer.\r
-;\r
-; ZTimerOff: Stops the long-period Zen timer and saves the timer\r
-; count and the BIOS time-of-day count.\r
-;\r
-; ZTimerReport: Prints the time that passed between starting and\r
-; stopping the timer.\r
-;\r
-; Note: If either more than an hour passes or midnight falls between\r
-; calls to ZTimerOn and ZTimerOff, an error is reported. For\r
-; timing code that takes more than a few minutes to execute,\r
-; either the DOS TIME command in a batch file before and after\r
-; execution of the code to time or the use of the DOS\r
-; time-of-day function in place of the long-period Zen timer is\r
-; more than adequate.\r
-;\r
-; Note: The PS/2 version is assembled by setting the symbol PS2 to 1.\r
-; PS2 must be set to 1 on PS/2 computers because the PS/2's\r
-; timers are not compatible with an undocumented timer-stopping\r
-; feature of the 8253; the alternative timing approach that\r
-; must be used on PS/2 computers leaves a short window\r
-; during which the timer 0 count and the BIOS timer count may\r
-; not be synchronized. You should also set the PS2 symbol to\r
-; 1 if you're getting erratic or obviously incorrect results.\r
-;\r
-; Note: When PS2 is 0, the code relies on an undocumented 8253\r
-; feature to get more reliable readings. It is possible that\r
-; the 8253 (or whatever chip is emulating the 8253) may be put\r
-; into an undefined or incorrect state when this feature is\r
-; used.\r
-;\r
-; ***************************************************************\r
-; * If your computer displays any hint of erratic behavior *\r
-; * after the long-period Zen timer is used, such as the floppy *\r
-; * drive failing to operate properly, reboot the system, set *\r
-; * PS2 to 1 and leave it that way! *\r
-; ***************************************************************\r
-;\r
-; Note: Each block of code being timed should ideally be run several\r
-; times, with at least two similar readings required to\r
-; establish a true measurement, in order to eliminate any\r
-; variability caused by interrupts.\r
-;\r
-; Note: Interrupts must not be disabled for more than 54 ms at a\r
-; stretch during the timing interval. Because interrupts\r
-; are enabled, keys, mice, and other devices that generate\r
-; interrupts should not be used during the timing interval.\r
-;\r
-; Note: Any extra code running off the timer interrupt (such as\r
-; some memory-resident utilities) will increase the time\r
-; measured by the Zen timer.\r
-;\r
-; Note: These routines can introduce inaccuracies of up to a few\r
-; tenths of a second into the system clock count for each\r
-; code section timed. Consequently, it's a good idea to\r
-; reboot at the conclusion of timing sessions. (The\r
-; battery-backed clock, if any, is not affected by the Zen\r
-; timer.)\r
-;\r
-; All registers and all flags are preserved by all routines.\r
-;\r
- DOSSEG\r
- .model small\r
- .code\r
- public ZTimerOn, ZTimerOff, ZTimerReport\r
-\r
-;\r
-; Set PS2 to 0 to assemble for use on a fully 8253-compatible\r
-; system; when PS2 is 0, the readings are more reliable if the\r
-; computer supports the undocumented timer-stopping feature,\r
-; but may be badly off if that feature is not supported. In\r
-; fact, timer-stopping may interfere with your computer's\r
-; overall operation by putting the 8253 into an undefined or\r
-; incorrect state. Use with caution!!!\r
-;\r
-; Set PS2 to 1 to assemble for use on non-8253-compatible\r
-; systems, including PS/2 computers; when PS2 is 1, readings\r
-; may occasionally be off by 54 ms, but the code will work\r
-; properly on all systems.\r
-;\r
-; A setting of 1 is safer and will work on more systems,\r
-; while a setting of 0 produces more reliable results in systems\r
-; which support the undocumented timer-stopping feature of the\r
-; 8253. The choice is yours.\r
-;\r
-PS2 equ 1\r
-;\r
-; Base address of the 8253 timer chip.\r
-;\r
-BASE_8253 equ 40h\r
-;\r
-; The address of the timer 0 count registers in the 8253.\r
-;\r
-TIMER_0_8253 equ BASE_8253 + 0\r
-;\r
-; The address of the mode register in the 8253.\r
-;\r
-MODE_8253 equ BASE_8253 + 3\r
-;\r
-; The address of the BIOS timer count variable in the BIOS\r
-; data segment.\r
-;\r
-TIMER_COUNT equ 46ch\r
-;\r
-; Macro to emulate a POPF instruction in order to fix the bug in some\r
-; 80286 chips which allows interrupts to occur during a POPF even when\r
-; interrupts remain disabled.\r
-;\r
-MPOPF macro\r
- local p1, p2\r
- jmp short p2\r
-p1: iret ;jump to pushed address & pop flags\r
-p2: push cs ;construct far return address to\r
- call p1 ; the next instruction\r
- endm\r
-\r
-;\r
-; Macro to delay briefly to ensure that enough time has elapsed\r
-; between successive I/O accesses so that the device being accessed\r
-; can respond to both accesses even on a very fast PC.\r
-;\r
-DELAY macro\r
- jmp $+2\r
- jmp $+2\r
- jmp $+2\r
- endm\r
-\r
-StartBIOSCountLow dw ? ;BIOS count low word at the\r
- ; start of the timing period\r
-StartBIOSCountHigh dw ? ;BIOS count high word at the\r
- ; start of the timing period\r
-EndBIOSCountLow dw ? ;BIOS count low word at the\r
- ; end of the timing period\r
-EndBIOSCountHigh dw ? ;BIOS count high word at the\r
- ; end of the timing period\r
-EndTimedCount dw ? ;timer 0 count at the end of\r
- ; the timing period\r
-ReferenceCount dw ? ;number of counts required to\r
- ; execute timer overhead code\r
-;\r
-; String printed to report results.\r
-;\r
-OutputStr label byte\r
- db 0dh, 0ah, 'Timed count: '\r
-TimedCountStr db 10 dup (?)\r
- db ' microseconds', 0dh, 0ah\r
- db '$'\r
-;\r
-; Temporary storage for timed count as it's divided down by powers\r
-; of ten when converting from doubleword binary to ASCII.\r
-;\r
-CurrentCountLow dw ?\r
-CurrentCountHigh dw ?\r
-;\r
-; Powers of ten table used to perform division by 10 when doing\r
-; doubleword conversion from binary to ASCII.\r
-;\r
-PowersOfTen label word\r
- dd 1\r
- dd 10\r
- dd 100\r
- dd 1000\r
- dd 10000\r
- dd 100000\r
- dd 1000000\r
- dd 10000000\r
- dd 100000000\r
- dd 1000000000\r
-PowersOfTenEnd label word\r
-;\r
-; String printed to report that the high word of the BIOS count\r
-; changed while timing (an hour elapsed or midnight was crossed),\r
-; and so the count is invalid and the test needs to be rerun.\r
-;\r
-TurnOverStr label byte\r
- db 0dh, 0ah\r
- db '****************************************************'\r
- db 0dh, 0ah\r
- db '* Either midnight passed or an hour or more passed *'\r
- db 0dh, 0ah\r
- db '* while timing was in progress. If the former was *'\r
- db 0dh, 0ah\r
- db '* the case, please rerun the test; if the latter *'\r
- db 0dh, 0ah\r
- db '* was the case, the test code takes too long to *'\r
- db 0dh, 0ah\r
- db '* run to be timed by the long-period Zen timer. *'\r
- db 0dh, 0ah\r
- db '* Suggestions: use the DOS TIME command, the DOS *'\r
- db 0dh, 0ah\r
- db '* time function, or a watch. *'\r
- db 0dh, 0ah\r
- db '****************************************************'\r
- db 0dh, 0ah\r
- db '$'\r
-\r
-;********************************************************************\r
-;* Routine called to start timing. *\r
-;********************************************************************\r
-\r
-ZTimerOn proc near\r
-\r
-;\r
-; Save the context of the program being timed.\r
-;\r
- push ax\r
- pushf\r
-;\r
-; Set timer 0 of the 8253 to mode 2 (divide-by-N), to cause\r
-; linear counting rather than count-by-two counting. Also stops\r
-; timer 0 until the timer count is loaded, except on PS/2\r
-; computers.\r
-;\r
- mov al,00110100b ;mode 2\r
- out MODE_8253,al\r
-;\r
-; Set the timer count to 0, so we know we won't get another\r
-; timer interrupt right away.\r
-; Note: this introduces an inaccuracy of up to 54 ms in the system\r
-; clock count each time it is executed.\r
-;\r
- DELAY\r
- sub al,al\r
- out TIMER_0_8253,al ;lsb\r
- DELAY\r
- out TIMER_0_8253,al ;msb\r
-;\r
-; In case interrupts are disabled, enable interrupts briefly to allow\r
-; the interrupt generated when switching from mode 3 to mode 2 to be\r
-; recognized. Interrupts must be enabled for at least 210 ns to allow\r
-; time for that interrupt to occur. Here, 10 jumps are used for the\r
-; delay to ensure that the delay time will be more than long enough\r
-; even on a very fast PC.\r
-;\r
- pushf\r
- sti\r
- rept 10\r
- jmp $+2\r
- endm\r
- MPOPF\r
-;\r
-; Store the timing start BIOS count.\r
-; (Since the timer count was just set to 0, the BIOS count will\r
-; stay the same for the next 54 ms, so we don't need to disable\r
-; interrupts in order to avoid getting a half-changed count.)\r
-;\r
- push ds\r
- sub ax,ax\r
- mov ds,ax\r
- mov ax,ds:[TIMER_COUNT+2]\r
- mov cs:[StartBIOSCountHigh],ax\r
- mov ax,ds:[TIMER_COUNT]\r
- mov cs:[StartBIOSCountLow],ax\r
- pop ds\r
-;\r
-; Set the timer count to 0 again to start the timing interval.\r
-;\r
- mov al,00110100b ;set up to load initial\r
- out MODE_8253,al ; timer count\r
- DELAY\r
- sub al,al\r
- out TIMER_0_8253,al ;load count lsb\r
- DELAY\r
- out TIMER_0_8253,al ;load count msb\r
-;\r
-; Restore the context of the program being timed and return to it.\r
-;\r
- MPOPF\r
- pop ax\r
- ret\r
-\r
-ZTimerOn endp\r
-\r
-;********************************************************************\r
-;* Routine called to stop timing and get count. *\r
-;********************************************************************\r
-\r
-ZTimerOff proc near\r
-\r
-;\r
-; Save the context of the program being timed.\r
-;\r
- pushf\r
- push ax\r
- push cx\r
-;\r
-; In case interrupts are disabled, enable interrupts briefly to allow\r
-; any pending timer interrupt to be handled. Interrupts must be\r
-; enabled for at least 210 ns to allow time for that interrupt to\r
-; occur. Here, 10 jumps are used for the delay to ensure that the\r
-; delay time will be more than long enough even on a very fast PC.\r
-;\r
- sti\r
- rept 10\r
- jmp $+2\r
- endm\r
-\r
-;\r
-; Latch the timer count.\r
-;\r
-\r
-if PS2\r
-\r
- mov al,00000000b\r
- out MODE_8253,al ;latch timer 0 count\r
-;\r
-; This is where a one-instruction-long window exists on the PS/2.\r
-; The timer count and the BIOS count can lose synchronization;\r
-; since the timer keeps counting after it's latched, it can turn\r
-; over right after it's latched and cause the BIOS count to turn\r
-; over before interrupts are disabled, leaving us with the timer\r
-; count from before the timer turned over coupled with the BIOS\r
-; count from after the timer turned over. The result is a count\r
-; that's 54 ms too long.\r
-;\r
-\r
-else\r
-\r
-;\r
-; Set timer 0 to mode 2 (divide-by-N), waiting for a 2-byte count\r
-; load, which stops timer 0 until the count is loaded. (Only works\r
-; on fully 8253-compatible chips.)\r
-;\r
- mov al,00110100b ;mode 2\r
- out MODE_8253,al\r
- DELAY\r
- mov al,00000000b ;latch timer 0 count\r
- out MODE_8253,al\r
-\r
-endif\r
-\r
- cli ;stop the BIOS count\r
-;\r
-; Read the BIOS count. (Since interrupts are disabled, the BIOS\r
-; count won't change.)\r
-;\r
- push ds\r
- sub ax,ax\r
- mov ds,ax\r
- mov ax,ds:[TIMER_COUNT+2]\r
- mov cs:[EndBIOSCountHigh],ax\r
- mov ax,ds:[TIMER_COUNT]\r
- mov cs:[EndBIOSCountLow],ax\r
- pop ds\r
-;\r
-; Read the timer count and save it.\r
-;\r
- in al,TIMER_0_8253 ;lsb\r
- DELAY\r
- mov ah,al\r
- in al,TIMER_0_8253 ;msb\r
- xchg ah,al\r
- neg ax ;convert from countdown\r
- ; remaining to elapsed\r
- ; count\r
- mov cs:[EndTimedCount],ax\r
-;\r
-; Restart timer 0, which is still waiting for an initial count\r
-; to be loaded.\r
-;\r
-\r
-ife PS2\r
-\r
- DELAY\r
- mov al,00110100b ;mode 2, waiting to load a\r
- ; 2-byte count\r
- out MODE_8253,al\r
- DELAY\r
- sub al,al\r
- out TIMER_0_8253,al ;lsb\r
- DELAY\r
- mov al,ah\r
- out TIMER_0_8253,al ;msb\r
- DELAY\r
-\r
-endif\r
-\r
- sti ;let the BIOS count continue\r
-;\r
-; Time a zero-length code fragment, to get a reference for how\r
-; much overhead this routine has. Time it 16 times and average it,\r
-; for accuracy, rounding the result.\r
-;\r
- mov cs:[ReferenceCount],0\r
- mov cx,16\r
- cli ;interrupts off to allow a\r
- ; precise reference count\r
-RefLoop:\r
- call ReferenceZTimerOn\r
- call ReferenceZTimerOff\r
- loop RefLoop\r
- sti\r
- add cs:[ReferenceCount],8 ;total + (0.5 * 16)\r
- mov cl,4\r
- shr cs:[ReferenceCount],cl ;(total) / 16 + 0.5\r
-;\r
-; Restore the context of the program being timed and return to it.\r
-;\r
- pop cx\r
- pop ax\r
- MPOPF\r
- ret\r
-\r
-ZTimerOff endp\r
-\r
-;\r
-; Called by ZTimerOff to start the timer for overhead measurements.\r
-;\r
-\r
-ReferenceZTimerOn proc near\r
-;\r
-; Save the context of the program being timed.\r
-;\r
- push ax\r
- pushf\r
-;\r
-; Set timer 0 of the 8253 to mode 2 (divide-by-N), to cause\r
-; linear counting rather than count-by-two counting.\r
-;\r
- mov al,00110100b ;mode 2\r
- out MODE_8253,al\r
-;\r
-; Set the timer count to 0.\r
-;\r
- DELAY\r
- sub al,al\r
- out TIMER_0_8253,al ;lsb\r
- DELAY\r
- out TIMER_0_8253,al ;msb\r
-;\r
-; Restore the context of the program being timed and return to it.\r
-;\r
- MPOPF\r
- pop ax\r
- ret\r
-\r
-ReferenceZTimerOn endp\r
-\r
-;\r
-; Called by ZTimerOff to stop the timer and add the result to\r
-; ReferenceCount for overhead measurements. Doesn't need to look\r
-; at the BIOS count because timing a zero-length code fragment\r
-; isn't going to take anywhere near 54 ms.\r
-;\r
-\r
-ReferenceZTimerOff proc near\r
-;\r
-; Save the context of the program being timed.\r
-;\r
- pushf\r
- push ax\r
- push cx\r
-\r
-;\r
-; Match the interrupt-window delay in ZTimerOff.\r
-;\r
- sti\r
- rept 10\r
- jmp $+2\r
- endm\r
-\r
- mov al,00000000b\r
- out MODE_8253,al ;latch timer\r
-;\r
-; Read the count and save it.\r
-;\r
- DELAY\r
- in al,TIMER_0_8253 ;lsb\r
- DELAY\r
- mov ah,al\r
- in al,TIMER_0_8253 ;msb\r
- xchg ah,al\r
- neg ax ;convert from countdown\r
- ; remaining to elapsed\r
- ; count\r
- add cs:[ReferenceCount],ax\r
-;\r
-; Restore the context and return.\r
-;\r
- pop cx\r
- pop ax\r
- MPOPF\r
- ret\r
-\r
-ReferenceZTimerOff endp\r
-\r
-;********************************************************************\r
-;* Routine called to report timing results. *\r
-;********************************************************************\r
-\r
-ZTimerReport proc near\r
-\r
- pushf\r
- push ax\r
- push bx\r
- push cx\r
- push dx\r
- push si\r
- push di\r
- push ds\r
-;\r
- push cs ;DOS functions require that DS point\r
- pop ds ; to text to be displayed on the screen\r
- assume ds:_TEXT\r
-;\r
-; See if midnight or more than an hour passed during timing. If so,\r
-; notify the user.\r
-;\r
- mov ax,[StartBIOSCountHigh]\r
- cmp ax,[EndBIOSCountHigh]\r
- jz CalcBIOSTime ;hour count didn't change,\r
- ; so everything's fine\r
- inc ax\r
- cmp ax,[EndBIOSCountHigh]\r
- jnz TestTooLong ;midnight or two hour\r
- ; boundaries passed, so the\r
- ; results are no good\r
- mov ax,[EndBIOSCountLow]\r
- cmp ax,[StartBIOSCountLow]\r
- jb CalcBIOSTime ;a single hour boundary\r
- ; passed-that's OK, so long as\r
- ; the total time wasn't more\r
- ; than an hour\r
-\r
-;\r
-; Over an hour elapsed or midnight passed during timing, which\r
-; renders the results invalid. Notify the user. This misses the\r
-; case where a multiple of 24 hours has passed, but we'll rely\r
-; on the perspicacity of the user to detect that case.\r
-;\r
-TestTooLong:\r
- mov ah,9\r
- mov dx,offset TurnOverStr\r
- int 21h\r
- jmp short ZTimerReportDone\r
-;\r
-; Convert the BIOS time to microseconds.\r
-;\r
-CalcBIOSTime:\r
- mov ax,[EndBIOSCountLow]\r
- sub ax,[StartBIOSCountLow]\r
- mov dx,54925 ;number of microseconds each\r
- ; BIOS count represents\r
- mul dx\r
- mov bx,ax ;set aside BIOS count in\r
- mov cx,dx ; microseconds\r
-;\r
-; Convert timer count to microseconds.\r
-;\r
- mov ax,[EndTimedCount]\r
- mov si,8381\r
- mul si\r
- mov si,10000\r
- div si ;* .8381 = * 8381 / 10000\r
-;\r
-; Add timer and BIOS counts together to get an overall time in\r
-; microseconds.\r
-;\r
- add bx,ax\r
- adc cx,0\r
-;\r
-; Subtract the timer overhead and save the result.\r
-;\r
- mov ax,[ReferenceCount]\r
- mov si,8381 ;convert the reference count\r
- mul si ; to microseconds\r
- mov si,10000\r
- div si ;* .8381 = * 8381 / 10000\r
- sub bx,ax\r
- sbb cx,0\r
- mov [CurrentCountLow],bx\r
- mov [CurrentCountHigh],cx\r
-;\r
-; Convert the result to an ASCII string by trial subtractions of\r
-; powers of 10.\r
-;\r
- mov di,offset PowersOfTenEnd - offset PowersOfTen - 4\r
- mov si,offset TimedCountStr\r
-CTSNextDigit:\r
- mov bl,'0'\r
-CTSLoop:\r
- mov ax,[CurrentCountLow]\r
- mov dx,[CurrentCountHigh]\r
- sub ax,PowersOfTen[di]\r
- sbb dx,PowersOfTen[di+2]\r
- jc CTSNextPowerDown\r
- inc bl\r
- mov [CurrentCountLow],ax\r
- mov [CurrentCountHigh],dx\r
- jmp CTSLoop\r
-CTSNextPowerDown:\r
- mov [si],bl\r
- inc si\r
- sub di,4\r
- jns CTSNextDigit\r
-;\r
-;\r
-; Print the results.\r
-;\r
- mov ah,9\r
- mov dx,offset OutputStr\r
- int 21h\r
-;\r
-ZTimerReportDone:\r
- pop ds\r
- pop di\r
- pop si\r
- pop dx\r
- pop cx\r
- pop bx\r
- pop ax\r
- MPOPF\r
- ret\r
-\r
-ZTimerReport endp\r
-\r
- end\r
-\1a
\ No newline at end of file
projects / 16.git / blobdiff