PnP r0.95 comments

Tue Jan 11 17:10:02 PST 1994

                      Subject:                              Time:  1:15 PM
  OFFICE MEMO         PnP r0.95 comments                    Date:  1/4/94

Unfortunately I will not be able to attend the meeting in Colorado Springs this 
week.  However, I will be available next week at the SCSI meeting.  I suggest we 
might want to schedule a meeting during that time to resolve further outstanding 
issues.  I can also be reached at my office, and would be happy to discuss these 
comments with anyone.

1.	Foreword

Please add Quantum to the list of companies that initially worked on the Plug 
and Play document (since we started the whole SCAM activity last spring).

2.	Hardware (section 5)

It may be a goodness to require SCSI-3 compliance, but I do not see the need in 
a standard that is primarily concerned with auto addressing and auto 
termination.  The SCSI committee is still trying to sort out what SPI compliance 
means.  If it is unnecessary, then I say drop it, or at least postpone its 
implementation until the industry is better equipped (say late '94).

3.	Connectors (section 5.1)

Do you really want to have no connector requirements for SCSI devices (i.e. bare 
drives)?  I suggest we focus on the 50 pin, 100 mil center devices since they 
are by far the most popular.  I hear people wanting to make provision for the 68 
pin high density connector, but I strongly resist making that the only option 
(we just started shipping those in 3.5" drives!).  And specifying two connectors 
WILL lead to more cabling confusion.

4.	System configurations (section 6)

We are still requiring the user to buy and install the external (non host 
adapter) terminator for the system.  This is done at the time that the first 
device is installed.  Why do that and not simply use the terminator on that 
device instead?  The device can be shipped with the terminator removed, but 
still available in the package.  That device should be put at then end of the 
cable for future expansion.  This is no worse that putting an external 
terminator at the end of the cable.

Also, switchable terminators are allowed on the host adapter, but why not the 
devices themselves?  Devices should be allowed to have switchable terminators.  
If you want, they can be specified as turned off by default, to be activated by 
a software protocol (to be defined at a later time).  In the meantime we can use 
the external terminator devices as currently specified.  But a path should be 
cleared for the day of switchable terminators totally under software control 
that should ultimately prove easier and cheaper to use.

In general, I think the terminators are still a real issue (unlike auto 
addressing).  The only solution I really like is switchable terminators with a 
software protocol.

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