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Conference 7.286::fddi

Title:	FDDI - The Next Generation

Moderator:	NETCAD::STEFANI

Created:	Thu Apr 27 1989
Last Modified:	Thu Jun 05 1997
Last Successful Update:	Fri Jun 06 1997
Number of topics:	2259
Total number of notes:	8590

1765.0. "how to enable FDX" by TPOV07::TONYCHENG () Wed Aug 02 1995 09:34


    Does anyone know how to enable full-duplex function for DEMFA controller
    that under VMS 5.5-2 and without snmp function ?

    our configuration is shown below :



                  +-------------------------------+
                  |           GIGASWITCH          |
                  +-------------------------------+
                     |    |    |     |    |    | 
                     |    |    |     |    |    |  FGL-4 CONTROLLER
                     |    |    |     |    |    | 
                     
                      VAX 7610 * 4 , VAX 6420 * 2 

                       OS   = VMS 5.5-2
                       FDDI = DEMFA ,  FW = V2.0
                       UCX  = N/A
                       
     Regards
     Tony Cheng

T.R	Title	User	Personal Name	Date	Lines
1765.1		STAR::STOCKDALE		`Thu Aug 03 1995 14:41`	10
	As far as I know, there is nothing the VMS driver has to do. All that is needed is to have V2.0 of the firmware in the DEMFA and connect it a port that supports full duplex. Not that there is any good reason to use full duplex on a DEMFA, unless you can get excited over a 10 to 15 mbit improvement. (The best I ever saw was around 110-115 mbits/sec - its hard to tell the DEMFA is running full-duplex since the difference is so small). - Dick
1765.2		STRWRS::KOCH_P	It never hurts to ask...	`Thu Aug 03 1995 15:22`	4
	I agree with .1, but even though it doesn't really increase thruput, wouldn't it have an effect on latency given you could be doing simultaneous xfer & rcv?
1765.3		STAR::STOCKDALE		`Fri Aug 04 1995 17:28`	5
	Right, there should be some difference there, although on a VAX I doubt the difference would be measurable (not enough computes and the driver implementation is less than optimal). - Dick
1765.4		TPOV07::TONYCHENG		`Tue Aug 08 1995 06:25`	7
	I got trouble because i told my customer, our FDX function should boost FDDI throughput. Do we have the DEMFA performance analysis report ? Where can find it ? Regards Tony Cheng
1765.5		STRWRS::KOCH_P	It never hurts to ask...	`Tue Aug 08 1995 09:19`	3
	The question is, was this testing only done with a VAX 6600? Was it rerun using an Alpha system? Or is it a limitation of the controller?
1765.6		STAR::STOCKDALE		`Tue Aug 08 1995 19:34`	1
	Its a DEMFA hardware limitation.
1765.7		STEVMS::PETTENGILL	mulp	`Mon Aug 21 1995 22:11`	17
	> I got trouble because i told my customer, our FDX function should boost > FDDI throughput. Do we have the DEMFA performance analysis report ? > Where can find it ? "boost FDDI throughput" relative to what? We measured an increased thruput over not-FDX when sending/receiving a high percentage of back-to-back 4500 byte packets. The only way to accomplish this is with MSCP server traffic to a lot of disks. Under these circumstances its possible to move from the FDDI and/or GIGAswitch backplane limit of 97-98 megabits up to the DEMFA DMA limit of 115-120 megabits. The DEMFA was designed a long time ago before full duplex was considered so it provided 10-20% added bandwidth to ensure that it wasn't the bottleneck. We also did some testing to see if we could demonstrate reduced latency, but I don't believe that we came up with anything convincing. Its difficult to do this was VAX systems since the clock resolution is so course (10ms).