Conference ssag::ask_ssag

6490.0. "8 Bit I/O module (BA35X-MG) usage?" by VAXRIO::CUPOLILLO () Tue Mar 18 1997 13:06

    
    
          Hi,
    
          I would like to check the instruction on the BA35X-MG (8-Bit I/O
    Module) to check if I not nisunderstand then.  I have two AlphaServers
    2000, with KZPAA, now I need to connect between these two Servers a 
    BA356 pedestal with five RZ28M-VW disks in it.  As the KZPAA is a
    narrow controller, and I intend to use the disks as narrow ones, I will
    use the BA35X-MG to have 8 bits inputs for the BA356, as the I/O module
    has two SCSI connectors JA1 and JB1, can I use these two connectors to
    connect each KZPAA to the I/O module or do I have to use an Y-conector
    (BN21V-03) on connector JA1 only and leave JB1 open?
    
          I am confused with the bus termination, I presume that the SCSI
    bus has to have terminations on both KZPAA which will be the ends of
    the bus.  So in this sense I have to use the I/O module in a way that
    its internal terminations do not count, to have this what is the right
    way to use the I/O module connectors JA1/JB1?
     
          Many thanks,
    
          Cupol

    Cupol,
    
    If you plug a cable into JB1 in the BA35X-MG, the internal terminator 
    on the BA356 will turn off.  You bus will now be terminated at both 
    ends (KZPAA) only.  
    
    Be careful with your bus length.  It must be 3 meters or less TOTAL 
    for Fast SCSI.  The BA356 is about 1m, so your TOTAL cable length
    should be 2m or less.
    
    				Bill