# RE: [SI-LIST] : How to simulate SCSI backplane with 15 slots?

From: Willis, Ken ([email protected])
Date: Fri Jan 12 2001 - 14:19:12 PST

Hi John,

What I have done is to basically set up a BIG topology sweep. You can use
0 ohm and 10 megohm resistors in the topology to represent when things are
plugged in or left open. Kick it off and go home and get some sleep. In the
morning dump the results to Excel, and start sorting by your specific
criteria like overshoot, settle delay, etc. Hopefully in doing this you will
be able to determine the worst case configurations you will have to deal
with.

When you have real Allegro board designs, you can plug them together
with DesignLinks in the worst-case configurations you found up front,
run the corners and get your worst-case margins.

Sounds simple but it is definitely a lot of work. My approach is to lean
heavily on the up front topology sweeps to cut the post-layout verification
work down to the handful of worst configurations.

Ken

-----Original Message-----
From: [email protected] [mailto:[email protected]]
Sent: Wednesday, January 10, 2001 4:00 AM
To: [email protected] (E-mail)
Subject: [SI-LIST] : How to simulate SCSI backplane with 15 slots?

Dear SI gurus,

One question regarding SI simulation for SCSI backplane. How do I define the
worst case of SCSI backplane with 15 slots for 15 SCSI drives?

Shall I do the SI simulation, theoretically, for all combinations of 15 SCSI
drives?
There are huge combinations -- the number of drives mixed with the number of
slots (location on the backplane). Based on my knowledge, I would like to
put drives on even spaces for the best case of SI simulation. for example,
three drives on slot 1st,8th, and 15th. For the worst case, intuitively, I
would like to put them on slot 1st,2nd, and 3rd because of far away from end
terminators.

The question is that how to assure the worst case for simulation? Or,
doing all combinations is only way to do even it is exhaustive.

Best Regards,

John Lin
Senior SI Engineer, Server Team, ARD4
Quanta Computer Inc.,Taiwan, R.O.C.
Email: [email protected]
Tel: 886+3+3979000 ext. 5183

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