ljlamers at aol.com
ljlamers at aol.com
Sat Apr 30 06:01:09 PDT 1994
TO: X3T10 Membership
FR: Larry Lamers
RE: Comments on SCAM
DATE: April 14, 1994
During the process of incorporating SCAM into SPI some
questions have arisen.
1) Should legacy, level 1, and level 2 host devices be
allowed on the same bus?
I think that this is highly desireable. If not, then level
2 host devices will find limited application. Currently Rev
5 of SCAM prohibits this, but the justification is not
2) Is a level 1 device required to recognize dominant
This one is debateable, but I believe the answer is no. Rev
5 of SCAM did not specifically require this.
3) Is a level 2 device required to have a current ID?
I believe the answer is yes to insure backward
4) Should the soft ID be saved to the saved ID to become
the current ID following the a subsequent reset condition or
The answer seems to be no - the soft ID is never remembered
by a device following a reset condition or a power-on
5) Is someone going to propose a mode page to set the
Many disk drives already support a vendor unique mode page
to set the SCSI ID. The new SCSI ID becomes the saved ID
following a reset condition or a power-on condition if the
save parameters bit is set. The current ID is determined by
first checking the non-volatile storage. If a saved ID
other than zero exists then the saved ID becomes the current
ID. If the saved ID is zero then the default ID set by the
jumpers/switches becomes the current ID.
The hard ID is the current ID of the device following a
The soft ID becomes the current ID if a SCAM protocol occurs
and assigns a soft ID to the device. The soft ID shall not
become the saved ID.
6) Can we get rid of the abhorent terminology and used
A SCAM master is really a SCAM initiator. A SCAM slave is
really a SCAM target.
7) Are all SCAM host adapters required to put out the bus
master contention code?
This has been a real debate - the document is ambiguous - or
rather seems to state both sides of the case - that a host
adapter at level one does not need to do bus master
contention but that all scam masters should do it. There is
a potential interoperability problem here.
Lawrence J. Lamers
Adaptec TEL: 408-945-8600 ext 3214
691 Milpitas Bvld FAX: 408-957-7193
Milpitas, CA 95035 EMAIL: LJLAMERS at ADAPTEC.COM
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