[Simh] CI750 tech docs and VAX firmware

[Timothe Litt]

I don't have time to dig up the details.  But TOPS-10/20 definitely
supported the CI.  It turned out not to be used much since IIRC despite
the high wire speed, thruput was better on the NI.  But the rationale
was something like if you had CI connectivity for storage, and an NI
(ethernet) issue, you had to have a means of managing the other cluster
nodes.  So DECnet of CI ensured you could set host, do task-task; whatever.

For some evidence, look at ntman.mac:

TABSR1:	TXNN T1,<.NTLIN&.NTCKT>	;Is it a LINE or a CIRCUIT?
	 JRST TABSR2		;No, don't bother checking Line type
	LOAD T2,NXLTY,+NMXVAR	;Get the Line type
	MOVE T2,[NTD.D		;Bit indicating DTE
		 NTD.K		; KDP
		 NTD.P		; DDP
		 NTD.C		; CI
		 NTD.N		; NI
		 NTD.R]-1(T2)	; DMR
	TDNN T2,NT.DEV(NT)	;Does this Parameter apply to this Line Type?


NMXN23:	STOR T1,LIDEV,+P2	;STORE IN CIRCUIT ID WE ARE BUILDING
	CALL NMXN28		;GET A NUMBER FROM THE STRING
	STOR T1,LIKON,+P2	;STORE AS KONTROLLER NUMBER IN CIRCUIT ID
	CALL NMXN28		;GET THE NEXT NUMBER FROM THE STRING
	STOR T1,LIUNI,+P2	;SAVE UNIT NUMBER
	CALL NMXN28		;GET NEXT NUMBER (IF ANY)
	STOR T1,LIDRP,+P2	;SAVE AS DROP NUMBER (PORT ON CI)
	MOVE T1,P2		;GET THE CIRCUIT ID WE JUST BUILT
	RETSKP			;RETURN SUCCESS.


;WE KNOW THAT ALL DEVICE NAMES ARE AT MOST 4 BYTES LONG, AND THUS FIT IN A WORD
	HRLI T2,(POINT 7,)	;WE STORE THE DATA IN 7 BIT BYTES INTERNALLY
	HRRI T2,KONNAM(T1)	;GET POINTER TO DEVICE NAME
NMXC20:	ILDB T1,T2		;GET A BYTE FROM THE DEVICE NAME
	JUMPE T1,NMXC21		;END OF STRING, FALL THROUGH
	IDPB T1,P2		;SAVE IT IN OUR DESTINATION DATA STRING
	AOJA T6,NMXC20		;INCREMENT NUMBER OF BYTES DEPOSITED
NMXC21:	MOVEI T1,"-"		;SEPERATOR
	IDPB T1,P2		;STORE IT
	AOJ T6,			;COUNT UP CHARACTER
	LOAD T1,LIKON,+P1	;GET THE KONTROLLER NUMBER
	PUSHJ P,NMXC28		;OUTPUT NUMBER IN DECIMAL
	MOVEI T1,"-"
	IDPB T1,P2		;STORE THE SEPARATOR
	AOJ T6,			;INCREMENT NUMBER OF BYTES
	LOAD T1,LIUNI,+P1	;GET THE UNIT NUMBER
	PUSHJ P,NMXC28		;OUTPUT THE NUMBER IN DECIMAL
	JN LILXC,+P1,NMXC22	;Jump if we are not dealing with a CIRCUIT
	LOAD T1,LIDEV,+P1	;GET THE DEVICE TYPE
	CAXE T1,LD.CIP		;IS IT A CI?
	JRST NMXC22		;NO, WE ARE DONE
	MOVEI T1,"."		;OUTPUT SEPERATOR
	IDPB T1,P2		;STORE IT
	AOJ T6,			;AND INCREMENT COUNT
	LOAD T1,LIDRP,+P1	;GET THE DROP NUMBER (PORT ON THE CI)
	PUSHJ P,NMXC28		;AND OUTPUT IT IN DECIMAL




On 09-Mar-17 13:00, Paul Koning wrote:
>> On Mar 9, 2017, at 12:27 PM, Timothe Litt <litt at ieee.org> wrote:
>>
>> ..
>> With respect to an earlier question about CI emulation:  The best approach may be to emulate it as multicast ethernet.  Setup a couple of groups for each star coupler.  Each coupler supports up to 32 nodes.  For VMS, half o them hosts, half storage.  CI is a 50Mb/s (might be 70, but I remember 50 from the initial doc) CSMA/CD bus.
> 70 Mb/s is the number I always saw.
>
>>  The cabling is redundant (A & B cables), so assign one MC group to each per star.  (Yes, there are DECnet drivers for on multiple OSs.  I think it was considered a multipoint medium with addresses related to (CI) node numbers rather than an ethernet (broadcast) - but it's been a while.)
> I don't think DECnet ever supported CI.  It certainly doesn't show up in the DECnet architecture specs anywhere.
>
> 	paul
>

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