Conference ssag::ask_ssag

6424.0. "Bus length and KZPDA questions" by TLE::REAGAN (All of this chaos makes perfect sense) Tue Feb 25 1997 07:53

    I've asked this in the ALPHASTATION500 conference and I thought I'd
    ask it here to get additional information.
    
    I have a brandnew Alphastation 500/500 with a BA364 external box
    connected with a BN31G-01 cable.  At the console level, the disks (a
    RZ28D in the system box and 3 RZ28Ds in the BA364) sometimes show up
    and sometimes disappear.  Sometimes the system disk (inside the system
    box) disappears on VMS during the boot process.  Once the system is
    running I will ocassionally get a few error log entries that don't show
    anything wrong (I can post them if you think that will help).  
    
    The answer I got in the ALPHASTATION500 is that my SCSI bus might
    be too long.  Somebody recommended a shorter cable (BN31G-0E) or
    another controller for the external bus.
    
    My questions are:
    
    1) From reading the various manuals, I think my SCSI bus length 
    is 2.75M (1.2M in the AS500, 0.55M in the BA364, and 1.0M in the
    cable).  Is 2.75M too close for comfort?  Is the 3.0M limit a
    guess and shorter ones can also cause problems?
    
    2) Looking for other controllers, I didn't see a PCI FWSE controller
    in the SOC.  I found references to the KZPDA in a couple of notesfile.
    Would that controller work in a Alphastation 500/500?  The KZPDA isn't
    in the SOC.
    
    Thanks for any additional info you can provide.
    
    				-John