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Conference mvblab::sable

Title:SABLE SYSTEM PUBLIC DISCUSSION
Moderator:COSMIC::PETERSON
Created:Mon Jan 11 1993
Last Modified:Fri Jun 06 1997
Last Successful Update:Fri Jun 06 1997
Number of topics:2614
Total number of notes:10244

2564.0. "One PCI bus or 2 ?" by ODIXIE::RREEVES () Mon Mar 31 1997 15:33

    Is there 1 PCI bus with 8 slots on an Alphserver2100 250 or 
    two different PCI busses with 4 slots each ?
    
    Thanks in advance.
    
    Regards,
    
    Ray
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2564.12100 vs. 2100ASOLVIT::BAZARNICKContemplating BuoyancyMon Mar 31 1997 16:135
    AlphaServer 2100 5/250 product has 8 EISA, 3 PCI. The PDI are on same
    bus.
    
    AlphaServer 2100A 5/250 Product has 8 PCI on one bus (there is a bridge
    chip midway), so 4 primary and 4 secondary PCI slots.
2564.2What's the difference ????ODIXIE::RREEVESMon Mar 31 1997 17:235
    So what's the difference between a primary and secondary PCI bus slot ?
    If we are going to install a second DE435-AA ethernet card does it
    matter if this is installed into one of the primary or seconday slots?
    
    
2564.3DECWET::VOBAMon Mar 31 1997 22:5120
    Re .2, generally speaking...  this is in response to the question
    "what's the difference [between primary and secondary PCI buses]?"
    
    Certain PCI adapters do not work properly when configured on n/th-dary
    PCI bus (other than primary) due to a number of different reasons. 
    Sometime it was because the device driver makes a bad assumption that
    the device is only configured on the primary PCI bus (#0), thus not
    looking for the devices on other PCI buses; or, due to incompatibility
    of the PCI bridge chip (being used to tie the buses together), certain
    PCI signals and data are not being forwarded (in either direction -
    to/from the system); or, other variations of the above.
    
    When a PCI adapter and associated driver have been qualified/verified
    to work properly on multiple PCI buses, it should not matter which bus
    it is on.  There have been discussions about performance, e.g. farther
    bridged PCI buses may create longer signal delays - but unless the I/O
    option in question is dealing with a hardware interface that can handle
    "fast" throughput, it'd tend to be an academic discussion.
    
    --svb
2564.4DE435-AA goes anywhereSOLVIT::BAZARNICKContemplating BuoyancyTue Apr 01 1997 17:2810
    From the SOC, the only current 2100A slot restrictions are as follows:
    
    KZPSA-BB 3 max for WNT, PB2GA-JB for WNT, and CCMAA-AA/BA mem channel
    for dUNIX.
    
    These are restricted to primary slots, and cannot be installed in PCI slots
    4,5,6 and 7 (THE ONES BEHIND THE BRIDGE).
    
    The DE435-AA is not restricted, and may be placed in any PCI slot.max
    qty is 4.
2564.5ThanksODIXIE::RREEVESFri Apr 04 1997 14:475
    Thank you all for the information.
    
    Regards,
    
    Ray