🚀 go-pugleaf

Hi - 3 x 6000/70, 1 x 6000/80 (Sequent S27,S81 respectively) + 
        PTX 1.1.1 here...

We, along with some of you out there in netland, have experienced problems
with the SCED card dropping packets.  Reprinted (without permission) in 
near entirety is Unisys' FCN for determining whether the SCED card should
be upgraded to rev 47:

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PROBLEM VERIFICATION

This test MUST be run on the U6000/70 or /80 system that is suspected
of having a data of traffic handling problem.  If this test indicates
that this FCN will solve this problem then the customer engineer must
call the Customer Service Support Center to get approval to order this
FCN.

1. This FCN has been generated to provide a solution to a specific high
density traffic handling problem on the 6000/70's and 6000/80's.  This
FCN is ONLY required if other systems on the Ethernet are transmitting
at or near the limits of the 10 megabit Ethernet standard (ie.
interframe spacing is at or near 9.6 microseconds).  THIS IS NOT AN
UPGRADE FOR PERFORMANCE ENHANCEMENT.  It will only help when Ethernet
packets are having to be retransmitted due to a source system
transmitting at or near the limits of the 10 megabit Ethernet standard.

2. The FCN is ONLY required if the SCED Ethernet is experiencing 1 or
more receiver overflows per 1000 good packets received.  This is
easily determined.

3. To determine if this problem exists on a customer's system, use the
following procedure.

Note: each SCED should be evaluated individually.

PTX 1.1.1 or 1.2 Operating Systems

[procedure for running ethstat -z to reset statistics, then ethstat to
to look at the statistics.  ratio calculated is "receiver overflows"
as a percentage of "good packets received".  if "receiver overflows" x 1000
is greater than "good packets received", Unisys recommends the rev 47
SCED card be installed.]
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of our four machines, three are on the local Ethernet LAN.  of these three,
one has had its SCED card replaced with a rev 47 SCED card (all cards
were rev 44 beforehand).  the percentage of receiver overflows to good
packets received for our SCED v44 systems is 0.0119% and 0.00882%, and
the percentage on our SCED v47 system is 0.002%, or a 90% reduction in the
rate of receiver overflows.  Hence, the v47 SCED significantly improves
the situation (for our site, anyway) but does not solve it altogether.
-- 

Pete Gregory       |  Internet: pete@wvus.org
UNIX SA            |  Bangpath: ames!elroy!wvus!pete
World Vision U.S.  |  Slowpath: 919 W. Huntington Dr., Monrovia, CA 91016