/******* MULTI8 BACKGROUND SCHEDULER *******

BSCOUNT,"B^100+"S&3777	/NAME IS "BS" (BACKGROUND SCHEDULER)
SSFLG,	400		/A TWO-PAGE TASK WITHOUT CONNECTS
XBSSWAP,BSSWAP
XBSSTRT,BSSTRT		/BS STARTS WITH READING FIRST BG
LONGBG,	0		/LATCH FOR LAST LONG BG, MUST BE ZERO INIT.
BS,	JMP I XBSSTRT

BSSFLG,	ISZ SSFLG	/SET THE SHORT SLICE FLAG
BSGO,	JMS BSKICK
	TAD I (BJOB	/SEE IF CURRENT BG IS A 'LONG'
	JMS DEFER	/ONE. IN THAT CASE REMEMBER
	AND (LONG	/HIM AS THE CURRENT LONG BG
	SNA CLA
	 JMP .+3
	TAD X
	DCA LONGBG
	TAD SSFLG
	SNA CLA		/SHORT SLICE ?
	 JMP BSLNG1	/NO
	DCA SSFLG	/RESET SHORT SLICE FLAG
	TAD (-SLICE1
BSWAT1,	JMS BSTAL
	 SKP		/KICKED
	 JMP BSLONG	/TIMEOUT
	TAD I (BJOB
	JMS DEFER
	AND BSMSK1
	SZA CLA
	 JMP BSNEXT	/CURRENT BG FINISHED, SELECT NEXT 1
	JMS BSKICK	/SEE IF IT HAS INCORE SET & KICK IT
	JMP BSWAT1

BSLONG,	TAD I (BJOB	/SHORT SLICE OF CURRENT BG EXPIRED,
	JMS DEFER
	AND (-LONG-1
	TAD (LONG	/SET HIS 'LONG' BIT
	DCA I X
	JMS BSCAN
	   INACTIVE BGSTOP BGERR LONG SWPERR LOGOUT BGBLOK
BSLNG1,	TAD (-SLICE2	/WAIT FOR LONG SLICE OR EVENT
	JMS BSTAL
	 NOP		/
BSNEXT,	JMS BSCAN	/SEARCH FOR A RUNNABLE INTERACTIVE BG
	   INACTIVE BGSTOP BGERR LONG SWPERR LOGOUT BGBLOK
	TAD LONGBG	/TAKE NEXT LONG BG
	JMS BSCAN	/
BSMSK1,	   INACTIVE BGSTOP BGERR SWPERR LOGOUT BGBLOK
	JMP BSLNG1
BSCAN,	0
	SNA		/START SCANNING AT (AC) OR (BJOB)
	 TAD I (BJOB
	DCA ZTEM1	/REMEMBER THIS
	CDTOIF		//
	TAD I BSCAN	//
	CDF MONFLD	/
	ISZ BSCAN
	DCA BSMASK
	TAD (-BGMAX	/SET UP COUNTER # OF BG'S
	DCA ZTEM7	/COUNTER
	TAD ZTEM1
BSSCAN,	TAD (UNEXT
	JMS DEFER
	JMS DEFER	/GET STATUS OF NEXT BG
	AND BSMASK
	SNA CLA
	 JMP BSFOUND
	TAD X
	ISZ ZTEM7	/IS ROBIN ROUND ?
	 JMP BSSCAN	/NO
	CLA
	JMP I BSCAN	/YES RETURN

BSFOUND,TAD I X		/
	AND (ONDISK
	SNA CLA		/IS HE ONDISK ?
	 JMP BSGO	/NO, NO NEED TO SWAP
	TAD I (BJOB
	DCA ZTEM1
	TAD I ZTEM1
	AND (EMULATE
	SNA CLA		/MAY CURRENT BG BE SWAPPED OUT ?
	 JMP I XBSSWAP	/WHAMMM !
	ACM1		/NO, SET FLAG FOR EMULATOR
	DCA I (BSFLAG	/AND WAIT TILL HE IS FINISHED
	JMP BSGO
BSMASK,
BSKICK,	0		/SUBROUTINE TO CHECK IF BG IS WAITING
	TAD I (BJOB	/FOR USLOT TO HEAR HE IS IN CORE NOW
	JMS DEFER
	AND (INCORE
	SNA 		/DID HE KNOW THAT HE WAS ON DISK ?
	 JMP I BSKICK	/NO, DON'T TELL HIM
	CMA		/YES, CLEAR HIS INCORE BIT AND  ...
	AND I X	
	DCA I X	
	TAD X	
	TAD (USLOT
	JMS DEFER
	DCA .+3		/KICK THE SLOT WHERE HE IS WAITING
	JMS MONITOR
	   SIGNAL
	   0
	JMP I BSKICK	/AND LET HIM GO
BSTAL,	0
	SZA		/SETUP OR RESUME WAITING
	 DCA BSCOUNT
BSTA1,	ACM1
	JMS MONITOR
	   WAIT
	   BSSLOT
	TAD (-2
	SZA CLA		/TIMEOUT? OR SIGNAL FROM EMULATORS?
	 JMP I BSTAL	/SIGNAL, RETURN IMMEDIATLY
	ISZ BSCOUNT	/JUST A CLOCK TICK. THE LAST ONE ?
	 JMP BSTA1	/NO, SLICE NOT YET DONE
	ISZ BSTAL	/YES, SLICE EXPIRED,
	JMP I BSTAL	/TAKE SECOND RETURN

PAGE
XBSSFLG,BSSFLG
BSTEMP,	0
BSSWAP,	TAD (ONDISK	/SWAP A BG TO DISK AND ANOTHER
	TAD I ZTEM1	/IN CORE
	DCA I ZTEM1	/SET THE ONDISK-BIT OF CURRENT BG
	TAD ZTEM1
	DCA BSTEMP	/REMEMBER HIM IN CASE THE WRITE GIVES ERRORS
	TAD X
	DCA I (BJOB	/INSTALL THE NEW BJOB
	TAD ZTEM1	/DTV3+2 MAY HAVE LOST IT'S VALUE,
	TAD (USWAP	/SO GET IT'S VALUE AGAIN.
	JMS DEFER
	DCA DTV1+2	/FILL IN THE WRITE REQUEST
	TAD DTV1+2
	TAD (SWAPLG^3%4-10	/50(RK8E) OR 20(REST)
	DCA DTV2+2
	ACM1
	DCA BSW1	/SET FIRST WAIT TO NO-OP
	DCA ERROR
	JMS BSDO	/WRITE OUT 8K
	   DTV1-.
	JMS BSDO
	   DTV2-.
IFZERO BGFLDS-4 <
IFZERO PDPTYP-PDP8E <AC0100=IAC BSW>
IFNZRO PDPTYP-PDP8E <AC0100=TAD (100>
	AC0100
	TAD DTV1+2
	DCA DTV5+2
	AC0100
	TAD DTV2+2
	DCA DTV6+2
	JMS BSDO
	   DTV5-.
	JMS BSDO
	   DTV6-.		>
BSSTRT,	CLA CLL
	CDF MONFLD
	TAD I (BJOB	/INITIALLY START READING FIRST BG
	TAD (USWAP
	JMS DEFER	/GET SWAP BLOCK # OF NEW BG
	DCA DTV3+2
	TAD DTV3+2
	TAD (SWAPLG^3%4-10	/50(RK8E) OR 20(REST)
	DCA DTV4+2
	JMS BSDO	/READ 8K
	   DTV3-.
	TAD ERROR
	SZA CLA
	 ISZ I BSTEMP	/SETSWPERR BIT OF OLD BG
	DCA ERROR
	JMS BSDO
	   DTV4-.
IFZERO BGFLDS-4 <
	AC0100
	TAD DTV3+2
	DCA DTV7+2
	AC0100
	TAD DTV4+2
	DCA DTV8+2
	JMS BSDO
	   DTV7-.
	JMS BSDO
	   DTV8-.		>
	JMS MONITOR
	   WAIT
BSW1,	   -1		/A NOP-WAIT THE FIRST TIME
	SZA CLA
	 ISZ ERROR	/SET ERROR INDICATOR
	TAD I (BJOB
	JMS DEFER
	AND (-ONDISK-1
	DCA I X		/CLEAR THE ONDISK BIT ( HE IS IN CORE NOW )
	TAD ERROR
	SZA CLA
	 ISZ I X	/SET SWPERR INDICATOR
	JMP I XBSSFLG
BSDO,	0		/ROUTINE THAT DOES TRANSFER REQUESTS
	CDTOIF		//
	TAD BSW1	//
	DCA BSW2	//SHIFT SLOT #
	TAD I BSDO	//
	TAD BSDO	//ADD RELOCATION OFFSET
	JMS MONITOR	//
	   CALL		//
	   "S^100+"Y&3777
	 JMP .-3	//BUSY ?
	CDF MONFLD	/
	DCA BSW1	/SLOT
	JMS MONITOR
	   WAIT
BSW2,	   -1		/A NOP-WAIT THE FIRST TIME
	SZA CLA
	 ISZ ERROR	/SET ERROR INDICATOR
	JMP I BSDO

DTV1,	4000+BGFLD	/WRITE,4K,FIELD 0, UNIT 0
	0		/START AT ZERO
	0		/BECOMES BLOCK #
DTV2,	4010+BGFLD	/WRITE,4K,FIELD 1, UNIT 0
	0
	0
DTV3,	0000+BGFLD	/READ, 4K,FIELD 0, UNIT 0
	0
	0
DTV4,	0010+BGFLD	/READ, 4K,FIELD 1, UNIT 0
	0
	0
IFZERO BGFLDS-4 <
DTV5,	4020+BGFLD
	0
	0
DTV6,	4030+BGFLD
	0
	0
DTV7,	0020+BGFLD
	0
	0
DTV8,	0030+BGFLD
	0
	0		>

ERROR,	0

$