80 pin SCSI hard drives.

Ted Mittelstaedt tedm at toybox.placo.com
Fri Feb 17 09:29:07 PST 2006


  The problem you have with the 80-pin to 68-pin adapters is this.
A lot of the el-cheapo adapters do not terminate the unconnected
data lines, that is when you get instability.  The better quality
adapters do terminate them and don't have instability problems.


>-----Original Message-----
>From: owner-freebsd-questions at freebsd.org
>[mailto:owner-freebsd-questions at freebsd.org]On Behalf Of Mark Ovens
>Sent: Friday, February 17, 2006 7:30 AM
>To: freebsd-questions at freebsd.org
>Subject: Re: 80 pin SCSI hard drives.
>Alfredo Finelli wrote:
>> I have 80 pin SCSI discs mounted in hot-swappable trays on a SCSI
>> backplane which takes care also of powering them up and of SCSI
>> termination.  This is one way of using them.
>> I also have the same drives in a different system connected
>to normal SCSI
>> LVD cable using small adaptors which have an 80 pin receptacle on one
>> side and a 68 pin SCSI connector plus 4 pin molex power
>connector on the
>> other, as well as jumpers to define SCSI id.  In this second case you
>> have to provide the required termination of the SCSI bus
>(e.g. using the
>> right terminated SCSI cable).
>So you can confirm that using these adaptors works OK? When I bought my
>SCSI drive (off eBay) there were more SCA drives for sale than 68-pin
>but doing some research about 80->68 pin adaptors I found a lot of
>people saying not to use them, including Adaptec:
>This from Adaptec's ASK knowledgebase http://tinyurl.com/b3ofa
>"Although there are adapters on the market converting 80 pin to 68 pin
>they are not supported by Adaptec or the hard drive
>manufacturers. These
>convertors can cause loss of signal integrity that may result in
>connectivity issues and data loss."
>This put me off getting a SCA drive. Now I'm looking for a
>another drive
>and SCA ones seem to be cheaper on eBay.
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