sys7.1-doc-wip/OS/TimeMgr/TimeMgr.a

;
;	Hacks to match MacOS (most recent first):
;
;	<Sys7.1>	  8/3/92	Removed <3> QuickTime patch code, and what looks like a total rewrite of
;							__MicroSeconds.
;				  9/2/94	SuperMario ROM source dump (header preserved below)
;

;
;	File:		TimeMgr.a
;
;	Contains:	The Macintosh OS Time Manager
;
;	Written by:	Gary G. Davidian
;
;	Copyright:	© 1988-1993 by Apple Computer, Inc., all rights reserved.
;
;	Change History (most recent first):
;
;	   <SM5>	 11/9/93	KW		added some eieioSTP macros.  Only expands for CygnusX1 ROM
;	   <SM4>	11/12/92	PN		Get rid of ≥ 020 conditionals for ROM builds
;        <3>     9/10/92    AEK     Roll in new _microseconds and PrimeTime fix from Quicktime 
;                                   code for _microseconds was already there, so just remove old one
;		 <2>	 3/27/92	JSM		Merge in Philip’s change: Export Labels for Patch roll-in.
;		 <1>						• Pre-SuperMario comments follow •
;		 <9>	 2/12/92	JSM		Moved this file to TimeMgr folder, keeping all the old
;									revisions.
;		 <8>	11/16/91	DTY		Checked in Wayne Meretzky’s new version of __MicroSeconds,
;									conditionalized for TheFuture.
;		 <7>	  9/9/91	JSM		Cleanup header.
;		 <6>	 9/22/90	dba		Break some routines into separate PROCs so they can be cut back
;									in the linked patch version. Also change conditionals so the the
;									linked patch version of the Time Mgr. is universal (does not
;									assume 68020 or existence of the Power Mgr. chip). This file is
;									now used as the source both of the Time Mgr. in ROM and of the
;									Time Mgr. patches.
;		 <5>	 9/19/90	BG		Removed <3>. 040s are behaving more reliably now.
;		 <4>	 7/25/90	GGD		Added support for the _MicroSeconds trap which returns a 64 bit
;									Microsecond counter which is usefull for timestamping and
;									timing. Deleted some Eclipse NOPs which would not be assembled
;									for 68040s
;		 <3>	 6/20/90	CCH		Added some NOPs for flaky 68040's.
;		 <2>	 1/12/90	CCH		Added include of “HardwarePrivateEqu.a”.
;	   <1.4>	11/13/89	MSH		Pmgr equates now in record format.
;	   <1.3>	 2/23/89	GGD		Stored the underflow retry adjustment constant in RAM to allow
;									better patching flexability. On systems with PowerManagers,
;									switch into fast mode in FreezeTime, and restore mode in
;									ThawTime, to reduce drift in the time critical section, and to
;									prevent a potential loop in the underflow path.
;	   <1.2>	 1/30/89	GGD		Added new features for BigBang and the new ROMs. This includes
;									support for extended time manager tasks, and improves accuracy
;									and reduces drift even more.
;	   <1.1>	11/10/88	CCH		Fixed Header.
;	   <1.0>	 11/9/88	CCH		Adding to EASE.
;	   <1.4>	10/16/88	GGD		Changed resolution to 20µs with range of 1 day. Improved long
;									term accuracy, and added initialization code to do runtime
;									timings to make it processor speed independent. Coded around the
;									bug in Rockwell VIA timers. Removed machine specific
;									conditionals in favor of the "Cpu" equate. Improved conversion
;									constants for better accuracy. Went back to having state in the
;									system heap.
;	  <•1.3>	 9/23/88	CCH		Got rid of inc.sum.d and empty nFiles
;	   <1.2>	 8/16/88	GGD		Added InitTimeMgr initialization routine. Changed usage of
;									TimeVars, is now head of active list, no state in SysHeap.
;	   <1.1>	  8/5/88	GGD		Completely re-written. Lots of bug fixes and new features.
;				 7/26/88	GGD		Completely re-wrote the Time Manager, replacing all of the code
;									and comments from the old version. This version fixes numerous
;									bugs, and adds several new features.
;	   <1.0>	 2/10/88	BBM		Adding file for the first time into EASE…
;

			TITLE	'Time Manager - Macintosh Time Manager'

;_______________________________________________________________________
;
;	Macintosh Time Manager.
;
;	Written by Gary G. Davidian, July 26, 1988.
;
;_______________________________________________________________________

			print	off

			load	'StandardEqu.d'
			include	'HardwarePrivateEqu.a'

			print	on,nomdir

		if forROM then
				use68020Opcodes: equ 1
				machine	MC68020
		else
			use68020Opcodes: equ 0
			machine	MC68020					; some 020 opcodes in stuff that is run-time determined
		endif

; globals in system heap (same RECORD in TimeMgrPatch.a; move it to an equate file if you like)

TimeMgrPrivate	record	0,increment			; time manager private storage
ActivePtr		ds.l	1					; pointer to soonest active request
TimerAdjust		ds.b	1					; number of VIA ticks used loading timer
TimerLowSave	ds.b	1					; low byte of VIA timer from last FreezeTime		<4>
RetryAdjust		ds.w	1					; number of via ticks for underflow retry
CurrentTime		ds.l	1					; number of virtual ticks since boot
BackLog			ds.l	1					; number of virtual ticks of ready tasks
**** NOTE: The ordering of the following 4 fields must not change (FreezeTime Depends on it)	<4>
HighUSecs		ds.l	1					; high 32 bits of microsecond count					<4>
LowUSecs		ds.l	1					; low 32 bits of microsecond count					<4>
FractUSecs		ds.w	1					; 16 bit fractional microsecond count				<4>
CurTimeThresh	ds.w	1					; CurrentTime threshold for updating µsec count		<4>
**** end of order dependent fields																<4>
PrivateSize		equ		*-TimeMgrPrivate	; size of this record
				endr

USecsInc		equ		$FFF2E035			; 65522.8758µsec	(16.16 fixed point)				<4>
ThreshInc		equ		3208				; = 3208 internal ticks 							<4>
			eject
;_______________________________________________________________________
;
;	The time manager maintains a linked list of tasks that are waiting for
;	their timer to run out.  The list is ordered by expiration time, with
;	ActivePtr pointing to the task with the earliest timeout.  The tmCount
;	field of the each task on the list contains the number of virtual ticks
;	a task must wait after the task in front of it expires.  For the task
;	at the head of the list, this is the time to wait after the VIA timer
;	expires.
;	The TimerAdjust variable is used to account for the number of VIA ticks
;	that go by while we are trying to load a new timer value.  This is
;	computed at runtime, so that it is processor speed independent.
;
;_______________________________________________________________________


;_______________________________________________________________________
;
;	User visible changes since Inside Macintosh Vol. 4 was published.
;
;	1)	tmCount field is a LONGINT, not an INTEGER (documentation error).
;
;	2)	RmvTime, and PrimeTime now correctly return a result code (noErr)
;		in register D0.  Numerous other bugs that were not as visible have
;		also been fixed.
;
;	3)	Time can be represented in microseconds as well as milliseconds.
;		Negative values represent negated microseconds. (Although microseconds
;		can be specified, the actual resolution of the time manager is
;		currently closer to 20 microseconds).
;
;	4)	The high order bit of qType is now a flag to indicate that the
;		task timer is active.  Set by PrimeTime, cleared when time expires
;		or RmvTime is called.  Initialized cleared by InsTime.
;
;	5)	tmAddr may be set to zero to indicate that no completion routine
;		should be called. (The flag mentioned above may be used to determine
;		if the time has expired).
;
;	6)	The completion routine is now passed a pointer (in register A1) to
;		the TMTask record associated with it.  This makes it more usable
;		under Multi-Finder.
;
;	7)	When RmvTime is called on an active task, the tmCount field will
;		be returned with the amount of remaining time that had not been
;		used (in negative microseconds, or positive milliseconds).  If
;		the task had already expired, tmCount will contain zero.  This
;		allows the Time Manager to be used to compute elapsed times, which
;		is useful for performance measurments.
;
;	8)	In order to provide better resolution than 1 millisecond, the maximum
;		delay time was reduced from about 24 days, to currently about 1 day.
;		Larger delay times may still be specified to PrimeTime, but they will
;		be converted to the largest possible time instead.
;
;	9)	Support for Extended Time Manager Tasks has been added, _InsXTime is
;		used to install them.  The new field tmWakeUp is used by the TimeMgr
;		to remember when a _PrimeTime is supposed to expire.  When _PrimeTime
;		is called, if tmWakeUp is non-zero, then the new wakeup time will be
;		relative to the old tmWakeUp, instead of relative to the current time.
;		This allows for drift free fixed frequency timing tasks, which is needed
;		by the Sound Manager.
;
;_______________________________________________________________________
			TITLE	'Time Manager - Equates'

TaskActiveBit		equ		7			; high bit of QType word is active flag
ExtendedTmTaskBit	equ		6			; indicates an extended TmTask record
T2IntBit			equ		5			; VIER/VIFR bit num for VIA Timer 2

;_______________________________________________________________________
;
;	Representations of time in the Time Manager.
;
;	Time is represented externally in two ways, both are stored in a longword,
;	if the value is positive, it represents milliseconds, and if it is
;	negative, it represents negated microseconds.  This representation is used
;	as the delay time input to PrimeTime, and as the unused remaining time
;	output by RmvTime.
;
;	The VIA1 Timer2 is the 16 bit hardware timer used by the time manager.
;	On all current machines, it decrements at a rate of 783360 Hz, and
;	generates an interrupt, and keeps counting, when it counts through zero.
;	This provides resolution of 1.276 µsec, and a range of 83.660 msec.
;
;	Internally the time manager represents time as a virtual unsigned 36 bit
;	VIA timer, which gives a range of about 1 day.  However, since we only
;	have 32 bits to store time in, we drop the low 4 bits of the timer,
;	which reduces the resolution by a factor of 16 to 20.425 µsec.
;
;	Converting between the external and internal forms of time is done by
;	multiplying by the proper fixed point constants, and shifting the binary
;	point of the 64 bit result to get just the integer portion of the result.
;	The computation of the 32 bit conversion constants requires 64 bit
;	intermediate results, and unfortunatly the assembler only provides 32
;	bit expression evaluation, so the proper constants were computed with
;	a 64 bit hex caculator, and hard coded here (yuck!).  These are not
;	"Magic Numbers", the formula for computing them is provided, so that
;	they may be re-computed if any of the parameters ever change.
;
;_______________________________________________________________________

TicksPerSec			equ		783360		; VIA Timer clock rate
TickScale			equ		4			; Internal time is VIA ticks >> TickScale

MsToIntFractBits	equ		26			; number of fraction bits in 64 bit result
*MsToInternal		equ		((TicksPerSec<<(MsToIntFractBits-TickScale))\
							+999)/1000
MsToInternal		equ		$C3D70A3E	; msec to internal time multiplier

UsToIntFractBits	equ		32			; number of fraction bits in 64 bit result
*UsToInternal		equ		((TicksPerSec<<(UsToIntFractBits-TickScale))\
							+999999)/1000000
UsToInternal		equ		$0C88A47F	; µsec to internal time multiplier

IntToMsFractBits	equ		32			; number of fraction bits in 64 bit result
*InternalToMs		equ		((1000<<(IntToMsFractBits+TickScale))\
							+TicksPerSec-1)/TicksPerSec
InternalToMs		equ		$053A8FE6	; internal time to msec multiplier

IntToUsFractBits	equ		27			; number of fraction bits in 64 bit result
*InternalToUs		equ		((1000000<<(IntToUsFractBits+TickScale))\
							+TicksPerSec-1)/TicksPerSec
InternalToUs		equ		$A36610BC	; internal time to µsec multiplier


			macro	;	Macro for interfacing with the MultAndMerge routine.
			Convert	&Multiplier,&FractionBits
			bsr.s	MultAndMerge			; input/output is D0
			dc.l	&Multiplier			; conversion multiplier
			if		&eval(&FractionBits)=32 then
			dc.l	0						; merge mask (low 32 bits all fraction)
			else
			dc.l	-1<<&FractionBits	; merge mask (some low bits not fraction)
			rol.l	#32-&FractionBits,d0	; position result after merge
			endif
			endm
			TITLE	'Time Manager - Remove Time Manager Task'

TimeMgr		proc	export

			export	__InsTime				; Install Time Manager Task
			export	__RmvTime				; Remove Time Manager Task
			export	__PrimeTime				; Initiate Time Manager Task Delay
			import	FreezeTime				; Stop timer
			entry	ThawTime				; Start timer (used by InitTimeMgr)
			entry	Timer2Int				; Interrupt handler (vector set up by InitTimeMgr)
			with	TimeMgrPrivate

;_______________________________________________________________________
;
;  Routine:		RmvTime
;  Inputs:		A0 - pointer to Time Manager Task to remove
;  Outputs:		D0 - error code (noErr)
;  Destroys:	none
;  Calls:		FreezeTime, ThawTime, MultAndMerge
;  Called by:	OsTrap dispatcher
;
;  Function:	Removes the specified Time Manager Task from the control
;				of the Time Manager.  If PrimeTime had been previously
;				called for this task, and the time has not expired yet,
;				the amount of unused time will be returned in the tmCount
;				field. The unused time will be represented in negated
;				microseconds, if it is not too large to fit within 32 bits
;				otherwise it will be represented in positive milliseconds.
;				Additionally, the TaskActiveBit of the QType field will
;				be cleared to indicate that the timer task is no longer
;				active.
;
;_______________________________________________________________________

			export  AfterFreezeTimeInRmvTime
__RmvTime									; a0-a2/d1-d2 saved by dispatcher
			move.l	d3,-(sp)				; save d3 also

			jsr		FreezeTime				; setup to manipulate time queue
AfterFreezeTimeInRmvTime
			moveq.l	#0,d2					; D2 : total time remaining
			lea		ActivePtr-Qlink(a2),a1	; A1 : previous := head
@SearchLoop	move.l	QLink(a1),d0			; D0 : next := previous.QLink
			beq.s	@NotActive				; if end, not an active task
			exg.l	a1,d0					; A1 : previous := next (save old previous)
			move.l	tmCount(a1),d1			; get delay between previous and next
			add.l	d1,d2					; add to total time remaining
			cmpa.l	a0,a1					; is this the one to remove?
			bne.s	@SearchLoop				; loop until it is found

			movea.l	d0,a1					; A1 : old previous
			move.l	QLink(a0),d0			; get successor to removee
			move.l	d0,QLink(a1)			; previous points to successor
			beq.s	@Removed				; if no successor, don't adjust time
			movea.l	d0,a1					; get pointer to successor
			add.l	d1,tmCount(a1)			; pass removees time to successor
@Removed	move.l	d2,d0					; setup total time remaining in D0

@NotActive									; at this point D0 is total time remaining
			sub.l	BackLog(a2),d0			; don't count the backlog
			bhs.s	@GotRemaining			; if still time remaining
			moveq.l	#0,d0					; otherwise, all backlog, return zero time
@GotRemaining
			bsr.w	ThawTime				; done manipulating time queue

			movea.l	d0,a1					; save a copy of internal time
			convert	InternalToUs,IntToUsFractBits	; convert internal to µsec
			neg.l	d0						; µsecs are passed negated
			bmi.s	@ConvertDone			; if it fits we're done

			move.l	a1,d0					; restore copy of internal time
			convert	InternalToMs,IntToMsFractBits	; convert internal to msec
@ConvertDone
			move.l	d0,tmCount(a0)			; return unused delay time

			move.l	(sp)+,d3				; restore saved d3
			moveq.l	#0,d1					; clear all of the flags
; (fall in)	bra.s	__InsTime				; mark task inactive, return with success
			TITLE	'Time Manager - Install Time Manager Task'

;_______________________________________________________________________
;
;  Routine:		InsTime
;  Inputs:		A0 - pointer to Time Manager Task to install
;  Outputs:		D0 - error code (noErr)
;  Destroys:	none
;  Calls:		none
;  Called by:	OsTrap dispatcher, RmvTime (falls into)
;
;  Function:	Initializes the fields of a Time Manager Task, to indicate
;				that it is inactive.
;
;  NOTE:	This routine is documented in Inside Machintosh Vol 4., and
;			was used by the old Time Manager to install the task on the
;			Time Manager queue.  In this version of the Time Manager, the
;			queue only contains active tasks, so installation is done by
;			_PrimeTime now.
;
;_______________________________________________________________________

__InsTime									; a0-a2/d1-d2 saved by dispatcher
			moveq.l	#$1F,d0					; mask to clear flag bits in QType
			and.b	QType(a0),d0			; clear the flags
			andi.w	#$0600,d1				; isolate 2 flag bits from trap word
			lsr.w	#4,d1					; position the 3 flag bits (high bit zeroed)
			or.b	d1,d0					; merge into QType high byte
			move.b	d0,QType(a0)			; save flags, mark the task initially inactive
			moveq.l	#noErr,d0				; return success
			rts								; all done
			TITLE	'Time Manager - Multiply 32 by 32'

;_______________________________________________________________________
;
;  Routine:		MultAndMerge
;  Inputs:		D0				- 32 bit multiplier
;				(return PC) 	- 32 bit multiplicand
;				(return PC+4)	- 32 bit merge mask
;  Outputs:		D0 - upper 32 bits of 64 bit product, merged with selected
;				bits of lower 32 bits of 64 bit product as specified by
;				merge mask.
;  Destroys:	A2, D1, D2, D3
;  Calls:		none
;  Called by:	PrimeTime, RmvTime
;
;  Function:	Performs a 32 by 32 bit multiply producing a 64 bit result.
;				Same function as the 68020 MULU.L D0,D0:D1 instruction.
;				The 64 bit product is then merged into a 32 bit result, by
;				using a merge mask which has bits set corresponding to which
;				bits in the low 32 bits of the product are to be merged into
;				the corresponding bit positions of the high 32 bits of the
;				product. If the bits specified in the merge mask an non-zero
;				in the high 32 bits of the product, then a result of all ones
;				will be returned to indicate overflow.
;				This routine is used to perform fixed point multiplication,
;				where the position of the implied binary point may vary.
;
;  Note:		D0 = A B,  D1 := C D.  Product is derived as follows.
;				      B*D
;				+   B*C
;				+   A*D
;				+ A*C
;
;_______________________________________________________________________

			macro
			mulud0d168000

			; result in d0, d1
			; trashes d2, d3

			move.l	d4,-(sp)				; preserve d4
			move.l	d1,d2					; D2 := C D
			move.l	d1,d3					; D3 := C D
			mulu.w	d0,d1					; D1 := B*D
			swap	d1						;
			swap	d3						; D3 := D C
			mulu.w	d0,d3					; D3 := B*C
			swap	d0						; D0 := B A
			ext.l	d0						; D0 := A (sign extended)
			move.w	d0,d4					; D4 := A
			beq.s	@ShortMul				; if A is zero, skip next 2 mults

			mulu.w	d2,d4					; D4 := A*D
			swap	d2						; D2 := D C
			mulu.w	d2,d0					; D0 := A*C
			add.l	d4,d3					; D3 := A*D + B*C
			clr.w	d4						;
			addx.w	d4,d4					; D4 := carry from A*D + B*C

@ShortMul	add.w	d3,d1					; add middle product to low product
			swap	d1						; D1 := low 32 bits of product
			move.w	d4,d3					; D3 := copy saved carry
			swap	d3						; D3 := high 17 bits of A*D + B*C
			addx.l	d3,d0					; D0 := high 32 bits of product
			move.l	(sp)+,d4				; restore d4

			endm

		export  MultAndMerge
MultAndMerge
			movea.l	(sp)+,a2				; pop return address
			move.l	(a2)+,d1				; get multiplicand

	if forROM then
			mulu.l	d0,d0:d1				; d0:d1 := d0*d1
	else

			tst.b	CPUFlag					; are we on a machine with long multiply?
			bz.s	@noLongMultiply
			mulu.l	d0,d0:d1				; d0:d1 := d0*d1
			bra.s	@didMultiply
@noLongMultiply
			mulud0d168000					; d0:d1 := d0*d1 (trash d2, d3)
@didMultiply

	endif

			move.l	(a2)+,d2				; get merge mask
			beq.s	@Done					; if zero, result in d0 is correct
			and.l	d2,d1					; get the non-fraction bits from d1
			add.l	d0,d2					; corresponding bits in d0 should be zero
			subx.l	d2,d2					; d2 = -1 if d0 overflowed, else zero
			or.l	d2,d0					; return d0 = -1 if overflow
			or.l	d1,d0					; merge bits from d1 into d0
@Done		jmp		(a2)					; return to code after constant list
			TITLE	'Time Manager - Prime Time Manager Task'

;_______________________________________________________________________
;
;  Routine:		PrimeTime
;  Inputs:		A0 - pointer to Time Manager Task to schedule
;				D0 - [long] if >= 0, Delay Time in positive milliseconds
;							if < 0,  Delay Time in negated microseconds
;  Outputs:		D0 - error code (noErr)
;  Destroys:	none
;  Calls:		FreezeTime, ThawTime, MultAndMerge
;  Called by:	OsTrap dispatcher
;
;  Function:	Schedules a Time Manager Task to run after the specified
;				Delay Time expires.  The Delay Time may be specified in
;				milliseconds, in which case, it must be a positive number,
;				or it can be specified in microseconds, in which case, it
;				must be negated first.
;				Additionally, the TaskActiveBit of the QType field will
;				be set to indicate that the timer task is currently active,
;				and will be cleared when the specified time has expired.
;
;  NOTE:	The Time Manager does not support delay times as long as the
;			maximum number of milliseconds that can be passed to this call.
;			If delay time specified is too large, then the maximum delay
;			time supported will be used instead.
;
;_______________________________________________________________________
			export	AfterFreezeTimeInPrimeTime
											; a0-a2/d1-d2 saved by dispatcher
__PrimeTime	move.l	d3,-(sp)				; save d3 also

;_______________________________________________________________________
;
; start of code from Quicktime patch
; attempts to keep backlog from becoming very large
;

	IF 0 THEN										; ex<3> <Sys7.1> Removed QuickTime patch
			btst.b	#ExtendedTmTaskBit, qType(a0)
			beq.s	@notExtended
			lea		3+tmReserved(a0), a1
			tst.l	tmWakeUp(a0)
			beq.s	@startNew
			tst.l	d0
			beq.s	@checkCount
@startNew:
			clr.b	(a1)
			bra.s	@notExtended
@checkCount:
			addq.b	#1, (a1)
			bpl.s	@notExtended
			bclr.b	#ExtendedTmTaskBit, qType(a0)
@notExtended:
	ENDIF											; ex<3> <Sys7.1> End of removed code

;
; end of code from Quicktime patch
;
;_______________________________________________________________________

			tst.l	d0						; see if +msec or -µsec
			bpl.s	@msec					; µsec are negated, msec pos

@usec		neg.l	d0						; get positive number of µsecs
			convert	UsToInternal,UsToIntFractBits	; convert µsec to internal
			bra.s	@ConvertDone			; join common code

@msec		convert	MsToInternal,MsToIntFractBits	; convert msec to internal
@ConvertDone
			jsr		FreezeTime				; setup to manipulate time queue
AfterFreezeTimeInPrimeTime
			bset.b	#TaskActiveBit,QType(a0); mark the task as active
			bne.s	@AlreadyActive			; if already on the queue don't touch it

			btst.b	#ExtendedTmTaskBit,QType(a0)	; check for extended tmTask
			beq.s	@AddToActive			; of standard tmTask, nothing special to do

			move.l	CurrentTime(a2),d2		; get current time
			move.l	tmWakeUp(a0),d1			; get wake time from last _PrimeTime
			beq.s	@SetNewWakeTime			; if not set, delay relative to CurrentTime
			sub.l	d2,d1					; d1 := time since/till last wakeup
			bpl.s	@WakeInFuture			; if time till, just add to it
			add.l	d1,d0					; subtract time since from desired delay
			bcs.s	@SetNewWakeTime			; if time still positive, use it

			add.l	d0,d2					; new wakeup := old + delay
			bne.s	@WakeupInPast			; zero is special wakeup value, don't allow it
			moveq.l	#1,d2					; use one instead of zero
@WakeupInPast
			move.l	d2,tmWakeUp(a0)			; update wakeup.
			move.l	d0,d1					; remember negated delay
			sub.l	d0,BackLog(a2)			; remember how late we are
			moveq.l	#0,d0					; for negative delay, use zero
			lea		ActivePtr-Qlink(a2),a1	; A1 : previous := head
			move.l	QLink(a1),d2			; D2 : next := previous.QLink
			beq.s	@Insert					; if empty, make it the head
			exg.l	a1,d2					; A1 : previous := next (save old previous)
			sub.l	d1,tmCount(a1)			; add backlog of new task to old first task
			exg.l	a1,d2					; restore prior previous and next ptrs
			bra.s	@Insert					; add it to the active list

@WakeInFuture
			add.l	d1,d0					; add time till desired delay
@SetNewWakeTime
			add.l	d0,d2					; new wakeup := old + delay
			bne.s	@StoreWakeup			; zero is special wakeup value, don't allow it
			moveq.l	#1,d2					; use one instead of zero
@StoreWakeup
			move.l	d2,tmWakeUp(a0)			; update wakeup.

@AddToActive
			add.l	BackLog(a2),d0			; run it after all pending tasks
			lea		ActivePtr-Qlink(a2),a1	; A1 : previous := head
@SearchLoop	move.l	QLink(a1),d2			; D2 : next := previous.QLink
			beq.s	@Insert					; if end, insert after previous
			exg.l	a1,d2					; A1 : previous := next (save old previous)
			move.l	tmCount(a1),d1			; get delay between previous and next
			sub.l	d1,d0					; subtract from our delay time
			bhs.s	@SearchLoop				; loop until our delay between prev and next

			add.l	d1,d0					; d0 := delay between previous and new
			sub.l	d0,d1					; d1 := delay between new and next
			move.l	d1,tmCount(a1)			; adjust next task delay time
			exg.l	a1,d2					; restore prior previous and next ptrs

@Insert		move.l	d2,QLink(a0)			; new task followed by next task
			move.l	d0,tmCount(a0)			; setup new task delay time
			move.l	a0,QLink(a1)			; previous task followed by new task

@AlreadyActive
			bsr.s	ThawTime				; done manipulating time queue
			move.l	(sp)+,d3				; restore saved d3
			moveq.l	#noErr,d0				; return success
			rts								; all done
			TITLE	'Time Manager - Timer 2 Interrupt Handler'

;_______________________________________________________________________
;
;  Routine:		Timer2Int
;  Inputs:		none
;  Outputs:		none
;  Destroys:	A0, A1, A2, A3, D0, D1, D2, D3
;  Calls:		FreezeTime, ThawTime, tmAddr service routine.
;  Called by:	VIA 1 system interrupt handler
;
;  Function:	Services the timer interrupt, and calls the service routine
;				if task at the head of the list has expired, or continues
;				it running if more time remaining.  If nothing on timer
;				list, just disables the timer.
;
;  NOTE:	The TaskActiveBit in the QType field will be cleared when the
;			task timer expires so that applications can poll the timer for
;			completion.  If the tmAddr field is zero, the service routine
;			will not be called. When the service routine is called, A0 points
;			to the service routine itself, and A1 points to the expired
;			Time Manager task.
;
;_______________________________________________________________________

			export  AfterFreezeTimeInTimer2Int
Timer2Int									; a0-a3/d0-d3 saved by IntHand
			jsr		FreezeTime				; stop the timer, adjust time remaining				<4>
AfterFreezeTimeInTimer2Int
			move.l	ActivePtr(a2),d0		; get pointer to first active timer task
			beq.s	ThawTime				; if nothing in queue, just exit

			movea.l	d0,a0					; A0 := pointer to timer task
			tst.l	tmCount(a0)				; see if timer expired
			bne.s	ThawTime				; if not, let it continue running

			move.l	QLink(a0),ActivePtr(a2)	; remove it from the active list
			bclr.b	#TaskActiveBit,QType(a0); mark the task as completed
			bsr.s	ThawTime				; start next timer running

			move.l	tmAddr(a0),d0			; get service routine address
			beq.s	@NoHandler				; if no service routine, just exit
			movea.l	a0,a1					; A1 := pointer to queue element
			movea.l	d0,a0					; A0 := address of service routine
			jmp		(a0)					; return through the service routine
@NoHandler	rts								; all done
			TITLE	'Time Manager - Thaw Time'

;_______________________________________________________________________
;
;  Routine:		ThawTime
;  Inputs:		A2 - ptr to TimeMgrPrivate
;				D3.hi - saved SR (interrupt priority)
;				D3.lo - value read from the low byte of the VIA timer masked
;						to virtual ticks.
;  Outputs:		none
;  Destroys:	D1, D2, A1, A2
;  Calls:		none
;  Called by:	RmvTime, PrimeTime, Timer2Int
;
;  Function:	Starts timer, based upon head of timer list, adjusts
;				time remaining for head of list.  Restores interrupt
;				priority level.
;
;_______________________________________________________________________

ThawTime	move.l	#$0000FFFF>>TickScale,d2; max range (internal form) of VIA timer
			add.b	TimerAdjust(a2),d3		; add in the timer loading overhead
			move.l	ActivePtr(a2),d1		; check pointer to first active timer task
			beq.s	@StartTimer				; if no tasks, just start timer with max

			movea.l	d1,a1					; point to head of active list
			move.l	tmCount(a1),d1			; get time remaining for head
			sub.l	BackLog(a2),d1			; remove as much backlog as possible
			bhs.s	@NoBacklog				; if tmCount >= BackLog
			neg.l	d1						; BackLog - tmCount
			move.l	d1,BackLog(a2)			; update backlog
			moveq.l	#0,d1					; run immediatly
			bra.s	@FindMax				; update timer
@NoBackLog	clr.l	BackLog(a2)				; no backlog remaining
@FindMax	cmp.l	d2,d1					; check remaining time against max
			bhs.s	@UseMax					; if remaining >= max, use the max instead
			move.l	d1,d2					; otherwise, use time remaining
@UseMax		sub.l	d2,d1					; remaining := remaining - timer value
			move.l	d1,tmCount(a1)			; update time remaining

@StartTimer	movea.l	VIA,a1					; get base address of VIA1
			lea		vT2C(a1),a1				; point to low byte of counter for speed
			move.w	d3,d1					; save copy of adjusted original low byte
@Retry		add.l	d2,CurrentTime(a2)		; update current time
			lsl.w	#TickScale,d2			; convert internal form to VIA form
			lea		vT2CH-vT2C(a1),a2		; point to high byte for speed

; *** Begining of time critical section
		eieioSTP
			sub.b	vT2C-vT2C(a1),d3		; see how many ticks of overhead used
		eieioSTP
			sub.w	d3,d2					; subtract out overhead ticks
			bls.s	@Underflow				; if less than 1 tick, fix it up

;	VIAs from Rockwell (which we have been shipping for several years) and possibly
;	other vendors have a bug.  If you load the counter high byte in the same clock
;	as the old counter value is counting through zero, when the new counter value
;	counts through zero the VIA will not generate an interrupt. To work around this
;	"feature", we first load a dummy non-zero value into the high byte of the counter,
;	and then load the value we really wanted.  This should allow enough time to
;	guarantee that it will not be counting through zero at the time we load the real
;	counter value.  This fixes the "AppleShare server hang problem".

		eieioSTP
			move.b	d1,vT2CH-vT2CH(a2)		; *** ROCKWELL VIA FIX, DON'T REMOVE ***
		eieioSTP
			move.b	d2,vT2C-vT2C(a1)		; setup timer low byte latch
		eieioSTP
	if use68020Opcodes then					; 68020 shifting is fast
			lsr.w	#8,d2					; get high byte of time
		eieioSTP
			move.b	d2,vT2CH-vT2CH(a2)		; load high byte of timer, start timer
		eieioSTP
	else									; 68000 shifting is slower than memory
			move.w	d2,-(sp)				; get high byte of time
		eieioSTP
			move.b	(sp)+,vT2CH-vT2CH(a2)	; load high byte of timer, start timer
		eieioSTP
	endif
; *** End of time critical section

	if forROM then
		if hasPowerMgr then
			movea.l	PMgrBase,a2				; PMgr gobals.
			cmpi.b	#1,PMgrRec.saveSpeedo(a2)	; see if we need to be idle
			bne.s	@RemainFast				; if not, remain running at fast speed.
			tst.w	Clock1M					; return processor to idle.
@RemainFast
		endif
	endif

			swap	d3						; get saved sr from high word
			move.w	d3,sr					; restore interrupt priority level
			rts								; all done

@Underflow	add.w	d2,d3					; recompute original delay value
			sub.b	d3,d1					; adjust initial timer low byte
			neg.w	d2						; make excess time positive
			movea.l	TimeVars,a2				; point to TimeMgrPrivate
			add.w	RetryAdjust(a2),d2		; round up before conversion, add in some extra time
			lsr.w	#TickScale,d2			; convert it to virtual ticks
			add.l	d2,BackLog(a2)			; remember how negative we are for next freeze
			move.w	d1,d3					; restore initial timer low byte
			bra.s	@Retry					; now go reload the timer
			endproc
			TITLE	'Time Manager - Read 64 bit MicroSecond counter'
;_______________________________________________________________________						<4>
;
;  Routine:		MicroSeconds
;  Inputs:		none
;  Outputs:		A0/D0 - 64 bit counter (A0=High, D0=Low)
;  Destroys:	none
;  Calls:		none
;  Called by:	OsTrap dispatcher
;
;  Function:	Returns the value of the 64 bit microsecond counter, which
;				is useful for timestamping.
;
;_______________________________________________________________________

__MicroSeconds: proc	export					; a0-a2/d1-d2 saved by dispatcher
			import	FreezeTime
			import	ThawTime

			with	TimeMgrPrivate
			
			move.l	d3,-(sp)

			jsr		FreezeTime

			move.b	TimerLowSave(a2),d1		; low byte of VIA timer
			neg.b	d1
			ror.l	#4,d1
			move.w	CurrentTime+2(a2),d1	; get low word of current time
			lea		CurTimeThresh(a2),a1	; point to CurTimeThresh

			sub.w	(a1),d1					; CurrentTime := CurrentTime - CurTimeThresh
			addi.w	#ThreshInc,d1			; compute additional time
			rol.l	#TickScale,d1			; convert to un-scaled VIA time
			mulu.w	#InternalToUs>>16,d1	; convert to microseconds
		if 32-IntToUsFractBits-TickScale <> 1 then
			lsl.l	#32-IntToUsFractBits-TickScale,d1	; align to form 16.16 fixed point result
		else
			add.l	d1,d1					; align to form 16.16 fixed point result
		endif
			add.w	-(a1),d1				; add in FractUSecs, set ccr.x to carry out
			move.l	-(a1),d0				; LowUSecs
			move.l	-(a1),a0				; HighUSecs
			clr.w	d1						; clear out fraction bits
			swap	d1						; get additional µsecs
			addx.l	d1,d0					; add additional time to LowUSecs
			subx.l	d1,d1					; -1 if ccr.x = 1, 0 if ccr.x = 0
			sub.l	d1,a0					; propagate carry into HighUSecs

			jsr		ThawTime

			move.l	(sp)+,d3
			rts

			endproc

			TITLE	'Time Manager - Freeze Time'

;_______________________________________________________________________
;
;  Routine:		FreezeTime
;  Inputs:		none
;  Outputs:		A2 - ptr to TimeMgrPrivate
;				D3.hi - saved SR (interrupt priority)
;				D3.lo - value read from the low byte of the VIA timer masked
;						to virtual ticks.
;  Destroys:	D1, D2, A1
;  Calls:		none
;  Called by:	RmvTime, PrimeTime, Timer2Int
;
;  Function:	Saves current interrupt priority level, disables all interrupts.
;				Reads the VIA timer 2, adjusts tmCount field of all active
;				Time Manager Tasks to reflect actual time remaining.
;
;_______________________________________________________________________

FreezeTime	proc	export

			with	TimeMgrPrivate

			move.w	sr,d3					; save interrupt priority level
			swap	d3						; sr -> high word, zero -> low word
			move.w	#$0100-(1<<TickScale),d3; setup virtual tick mask
			movea.l	VIA,a1					; get base address of VIA1
			lea		vT2CH(a1),a1			; point to timer high byte for speed
			movea.l	TimeVars,a2				; point to TimeMgrPrivate
			ori.w	#$0700,sr				; disable all interrupts
	if forROM then
		if hasPowerMgr then
		eieioSTP
			tst.w	Clock16M				; force processor out of idle.
		eieioSTP
		endif
	else

			; NOP this out on machines without Power Mgr. chips

			export	PoundThreeNOPsHereIfNoPowerMgr
PoundThreeNOPsHereIfNoPowerMgr:
		eieioSTP
			tst.w	Clock16M				; force processor out of idle.
		eieioSTP

	endif

;	The VIA Timer is constantly decrementing, and after the high byte is read, but
;	before the low byte is read, the low byte may decrement from 00 -> FF, which
;	would mean that the high is off by one, which would be an error of 256 ticks.
;	By reading the high byte twice, we can detect and correct this situation.
;	We also correct for the case where the high byte counted from 00 -> FF, in which
;	case the interrupt pending bit may have been incorrect at the time we read it.

		eieioSTP
			move.b	vT2CH-vT2CH(a1),d2		; get high byte of counter
		eieioSTP
			moveq.l	#1<<T2IntBit,d1			; setup mask to check int pending
		eieioSTP
			and.b	vIFR-vT2CH(a1),d1		; get interrupt pending bit
		eieioSTP
			neg.l	d1						; d1.hi := -1 if int pending, else 0
	if use68020Opcodes then					; 68020 shifting is fast
			move.b	d2,d1					; insert timer high byte
			lsl.w	#8,d1					; position it in the right place
	else									; 68000 shifting is slower than memory
			move.b	d2,-(sp)				; insert timer high byte
			move.w	(sp)+,d1				; position it in the right place
	endif
		eieioSTP
			move.b	vT2C-vT2CH(a1),d1		; insert timer low byte
		eieioSTP
			sub.b	vT2CH-vT2CH(a1),d2		; see if high byte changed
		eieioSTP
			beq.s	@TimeOK					; if not, time is correct

			subx.l	d2,d2					; d2 := -1 if counted through zero
			or.l	d2,d1					; update sign bits
	if use68020Opcodes then					; 68020 shifting is fast
		eieioSTP
			move.b	vT2CH-vT2CH(a1),d1		; re-read timer high byte
		eieioSTP
			lsl.w	#8,d1					; position it in the right place
	else									; 68000 shifting is slower than memory
		eieioSTP
			move.b	vT2CH-vT2CH(a1),-(sp)	; re-read timer high byte
		eieioSTP
			move.w	(sp)+,d1				; position it in the right place
	endif
		eieioSTP
			move.b	vT2C-vT2CH(a1),d1		; insert timer low byte
		eieioSTP
@TimeOK
		eieioSTP
			move.b	d1,TimerLowSave(a2)		; save low byte of VIA timer						<4>
			moveq.l	#(1<<TickScale)-1,d2	; prepare to round to virtual ticks
			add.l	d2,d1					; if virtual tick not complete, don't count it
			and.b	d1,d3					; save VIA timer truncated to virtual ticks
			asr.l	#TickScale,d1			; convert ticks to internal time form
			sub.l	d1,CurrentTime(a2)		; update current time

			move.w	CurrentTime+2(a2),d2	; get low word of current time						<4>
@chkThresh	lea		CurTimeThresh(a2),a1	; point to CurTimeThresh							<4>
			cmp.w	(a1),d2					; see if next threshold has been reached			<4>
			bmi.s	@threshOK				; if not reached yet, don't need to increment		<4>
			addi.w	#ThreshInc,(a1)			; update the next threshold							<4>
			addi.l	#USecsInc,-(a1)			; update microsecond counter (low word, and fract)	<4>
			bcc.s	@chkThresh				; if no carry to prop, see if thresh adjusted		<4>
			addq.w	#1,-(a1)				; propagate the carry								<4>
			bcc.s	@chkThresh				; if no carry to prop, see if thresh adjusted		<4>
			addq.l	#1,-(a1)				; propagate the carry								<4>
			bra.s	@chkThresh				; see if threshold adjusted							<4>
@threshOK									;													<4>
			move.l	ActivePtr(a2),d2		; get pointer to first active timer task
			beq.s	@UpdateBacklog			; if no active tasks, no backlog (d2=0)

			movea.l	d2,a1					; setup pointer to task at head
			moveq.l	#0,d2					; assume new backlog will be zero
			sub.l	BackLog(a2),d1			; adjust the timer, account for backlog
			bpl.s	@Early					; extra time, no backlog of any kind

			add.l	tmCount(a1),d1			; tmCount := tmCount - backlog
			bcs.s	@UpdateHead				; if no remaining backlog, use remaining count
			sub.l	d1,d2					; setup remaining backlog
			moveq.l	#0,d1					; no remaining time
@UpdateHead	move.l	d1,tmCount(a1)			; setup new time remaining
@UpdateBacklog
			move.l	d2,BackLog(a2)			; update backlog time, if any
			rts								; all done

@Early		add.l	tmCount(a1),d1			; add excess time to time remaining
			bra.s	@UpdateHead				; update the time remaining counter
			endproc
			TITLE	'Time Manager - Initialize Time Manager'

;_______________________________________________________________________
;
;  Routine:		InitTimeMgr
;  Inputs:		none
;  Outputs:		none
;  Destroys:	none
;  Calls:		none
;  Called by:	StartInit
;
;  Function:	Allocates and initializes the Time Manager's global data
;				structures at system boot time.  Sets up VIA 1 Timer2
;				interrupt handler.  Computes the timer adjustment value
;				at runtime, since it is processor speed dependent.
;
;_______________________________________________________________________

InitTimeMgr	proc	export

			import	Timer2Int
			import	ThawTime
			with	TimeMgrPrivate

@SavedRegs	reg		a0-a4/d0-d5				; registers to preserve
			movem.l	@SavedRegs,-(sp)		; save the registers

			moveq.l	#PrivateSize,d0			; size to allocate
			_NewPtr	,SYS,CLEAR				; allocate and clear the structure
			move.l	a0,TimeVars				; setup pointer to private storage
			movea.l	a0,a2					; setup for ThawTime

	if forROM then
			move.w	#(1<<(TickScale-1))\	; round up before conversion
					+(1<<TickScale),RetryAdjust(a2)	; add in some extra time
	else
			moveq	#(1<<(TickScale-1))\	; round up before conversion
					+(2<<TickScale),d0		; add in some extra time (value for 68000)
			tst.b	CPUFlag					; what processor do we have?
			bz.s	@gotRetryAdjust			; 68000, use value computed above
			moveq	#(1<<(TickScale-1))\	; round up before conversion
					+(1<<TickScale),d0		; add in some extra time (value for 68020)
@gotRetryAdjust
			move.w	d0,RetryAdjust(a2)		; store the computed value
	endif

			lea 	Timer2Int,a1			; get interrupt handler address
			move.l	a1,Lvl1DT+(T2IntBit*4)	; put into interrupt table

			move.w	sr,-(sp)				; save interrupt level
			ori.w	#$0700,sr				; disable interrupts

			movea.l	Via,a4					; get VIA pointer
			lea		vT2C(a4),a1				; point to low byte of timer 2 for speed
			lea		vT1C(a4),a3				; point to low byte of timer 1 for speed
			lea		vACR(a4),a4				; point to AUX control reg for speed

			moveq.l	#-$80+(1<<T2IntBit),d1	; enable timer 2 interrupts
		eieioSTP
			move.b	d1,vIER-vT2C(a1)		; initialize the interrupt enable bit
		eieioSTP

			moveq.l	#~(1<<5),d5				; mask to set timer 2 into timed interrupt mode
		eieioSTP
			and.b	vACR-vACR(a4),d5		; save old AUX control reg
		eieioSTP
			moveq.l	#%00111111,d0			; force timer 1 into one-shot mode
			and.b	d5,d0					; clear the bits
		eieioSTP
			move.b	d0,vACR-vACR(a4)		; setup temporary AUX control reg
		eieioSTP
			moveq.l	#0,d3					; setup timer low byte value
			move.w	sr,d3					; get sr
			swap	d3						; sr in high word

		eieioSTP
			move.b	d1,vT1CH-vT1C(a3)		; load and start timer 1
		eieioSTP
			move.b	d1,vT2CH-vT2C(a1)		; load and start timer 2
		eieioSTP
			move.b	vT2C-vT2C(a1),d0		; get timer 2 low byte
		eieioSTP
			sub.b	vT1C-vT1C(a3),d0		; get initial timer skew
		eieioSTP
			jsr		ThawTime				; run the critical section, start timer
		eieioSTP
			move.b	vT2C-vT2C(a1),d1		; get timer 2 low byte
		eieioSTP
			sub.b	vT1C-vT1C(a3),d1		; get final timer skew
		eieioSTP

			sub.b	d0,d1					; don't count initial skew
			subi.w	#(($FFFF>>TickScale)<<TickScale),d1	; subtract out loaded timer value
			move.b	d1,TimerAdjust(a0)		; setup the fudge factor

		eieioSTP
			move.b	d5,vACR-vACR(a4)		; restore AUX control reg
		eieioSTP
			st		vT2CH-vT2C(a1)			; load and start timer 2
		eieioSTP
			move.w	(sp)+,sr				; restore interrupt level
			movem.l	(sp)+,@SavedRegs		; restore the registers
			rts								; Time Manager is initialized
			endproc
			end