multiple scsi device

[Simon Shapiro]

Hi Timothy Phan;  On 25-Aug-97 you wrote: 
>  Hi,
>  
>    I hope that I'm sending this problem to the right group.  Is there
>    some limitation or restriction on connect multiple scsi
>    devices and lenght of the scsi cable onto the adaptec?
>  
>    I'm currently have 2 internal harddrive, an internal
>    CDROM, and 2 external harddrive (total of 5) connected to the
>    adaptec control.  Everything is recognized by the
>    control in Linux without any problem.  In the last
>    few days,  I've tried to add one addition external
>    harddrive (to make it 6 in total) and it is not being
>    recognized.
>  
>    If I removed one of the other, then it would be ok.
>    I've check the SCSI ID for each and they all have
>    its own uniq ID.  All the cable I used seem to be OK because
>    if it is hooked up individually, then no problem.
>    Each of the external cable is about 2 feet in length  and
>    the internal cable has 7 connector and I do not remember
>    its length.

Justin is THE expert on the Adaptec.  From my limited experience, I am
peasently surprised 5 devices work reliably.  Generally, for Single-Ended
SCSI, ultra (20MHz) speeds, about 5 feet, 4 devices, active termination and 
at least two inches between devices is about right.

>From the symptoms you describe, you just found out what we all knew all the
time :-)

Simon

Yes, there are exceptions.  I had 8 SCSI UW SE devices on an Adaptec
2940UW.  They worked like that for several months.