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Conference ssag::ask_ssag

Title:Ask the Storage Architecture Group
Notice:Check out our web page at http://www-starch.shr.dec.com
Moderator:SSAG::TERZAN
Created:Wed Oct 15 1986
Last Modified:Fri Jun 06 1997
Last Successful Update:Fri Jun 06 1997
Number of topics:6756
Total number of notes:25276

6472.0. "Wide/Narrow negotiation, fact or fiction?" by KEIKI::WHITE (MIN(2�,FWIW)) Wed Mar 12 1997 15:49

    
    	I have heard some people say that putting a narrow drive in a wide
    only subsystem will cause all wide drives to perform in 8 bit mode.
    
    	I have also seen discussions about how the contoller should 
    negotiate with the drives for the width. i.e. 8 bit or 16 bit, and
    then talk narraow to narrow drives and wide to wide drives.
    
    	Are both statements correct?
    
    						Bill
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6472.1LEFTY::CWILLIAMSCD or not CD, that's the questionThu Mar 13 1997 07:248
    The first staement is incorrect.
    
    There were some older SW drives which would prevent wide operation due
    to design problems in the flex cables, but we have not made those for a
    couple of years.
    
    Chris
    
6472.2I wish I had a nickle,,,,SUBSYS::VIDIOT::PATENAUDEAsk your boss for ARRAY's...Thu Mar 13 1997 07:4018
>    	I have heard some people say that putting a narrow drive in a wide
>    only subsystem will cause all wide drives to perform in 8 bit mode.

False. Wide is something that a wide controller negotiates on a per device basis.

The problem chris eluded to in -.1 dealt with pre-12/94 SBB's having the upper 8
bits grounded on the flex. This in turn caused the wide drives to disapper when
a narrow drive was placed on the bus.

>    	I have also seen discussions about how the contoller should 
>    negotiate with the drives for the width. i.e. 8 bit or 16 bit, and
>    then talk narraow to narrow drives and wide to wide drives.

Close, you do not negotiate narrow. You negotiate wide, the default is narrow,
so if the device wll not habla wide you stay at default.

roger.