At 10:25 AM -0400 4/26/02, Tom Roth wrote:
>  > ----------
>>  From:       Frank Myers
>>  Reply To:   PowerBooks
>>  Sent:       Thursday, April 25, 2002 8:53 PM
>>  To: [EMAIL PROTECTED]
>>  Subject:    Re: SCSI Ethernet adapters - daisy chain?
>>
>>
>>  Yep, I've done it on a Asante Micro EN/SC adapter. Pls note that the
>>  faster device should go on first with the slowest, like a scanner, going
>>  last.
>>
>I was always under the impression that the entire SCSI chain will 
>only be as fast as the slowest device on the chain as the card has 
>to drop down it's speed to match the slowest device.

0 for 2.  The speed of the device doesn't affect it's order in the 
chain.  The relative speeds of different SCSI devices vary in their 
AVERAGE speed, but generally their PEAK speed is the same.  When a 
device sends a block of data, say 256 bytes, most devices send it at 
the same speed, somewhere near the maximum speed for that SCSI bus. 
A "slower" device sends them less often so it has a lower average 
speed.  Thus putting a faster device closer doesn't make a difference 
as the actual data is moving at the same speed as a slower device.

The only time the the actual bus speed slows down for a slower device 
is when using a fast and/or wide bus with a slow and/or narrow 
device.  And it only slows down for that access, for other devices it 
operates at the speed appropriate for those devices.  In the case of 
using an ASante EN/SC adapter, I don't think we are talking about a 
machine with a fast OR wide bus.


-- 
Clark Martin
Redwood City, CA, USA
Macintosh / Internet Consulting
[EMAIL PROTECTED]

"I'm a designated driver on the Information Super Highway"

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