Conference 7.286::fddi

2070.0. "DEFXU-BA == DEFXU-AA ????" by PRIVAT::OTTO (getting better all the time) Wed Jun 19 1996 03:35

Hello,

can someone explain what's the possible difference between a DEFXU-AA 
and a DEFXU-BA is (only layout or functional as well ???)

The story behind this question is as follows:

the customer has two Alphaserver 1000 4/233 equipped with a DEFEA-UA
running OpenVMS V6.2-1H2 that are linked to a DECconcentrator 900MX
via UTP-FDDI. (DEFXU-AA)

When they use DEFXU-BA instead of DEFXU-AA they get intermittend Link
errors until the Interface goes into a Link confidence test which breaks
all the network connections.
It took us awhile to isolate this problem down to the MOD PMD's 
When Field Service replaced the first MOD PMD, they accidently 
got a DEFXU-AA which fixed the problem on one system.

So both systems now have -AA mod pmds (which replaced -BA's)
and are now both working with the -AA's in place. This does
cure all the customer's problems related to the mod pmd's.

The customer is happy, but worried that he might go thru all of this
again in case one of the -AA modules dies and he has to replace it.

Since logistic tells us the -AA has been replaced by the -BA variant
it always takes special "action" to get the -AA variant.


Any idea's hints ??

OTTO

    More than likely there was something wrong with the last DEFXU-BA
    module you had. All FS did was to swap out a defective card and replace
    it with a working one. It's really that simple.
    
    The history of the DEFXU-AA/-BA is this: the -AA was introduced in '93
    and was primarily a discrete design. It worked OK, but it did not have
    the margin i wanted not did it operate beyond 40C (ambient). The -BA
    replaced the -AA in '94 and it used a single-chip solution for the UTP
    interface. This module had plenty of margin (that is, it would work
    well beyond 100m of Cat 5 UTP cable) and it had a temperature range of
    beyond 60C (although our requirements only go as high as 50C). So, in
    every measureable way, the -BA is superior to the -AA.
    
    bill
    DEFXU-AA/-BA designer

Hello Bill,

that was exactly the answer I was looking for.
Thank You very much.

OTTO