[Tfug] SCSI disks

Mon Aug 20 22:14:57 MST 2007

IMHO this problem / thread is way too complicated. Granted,
the topic can be pain in the ass.

IIRC, the problem was find a SCSi drive to fit a 50 pin 8bit
narrow SCSI host adapter. Correct?

I have / had some SCA drive adapters that had connectors to
attach 50 pin and 68 pin cables to. Also, IIRC the adapters
had places for terminating resistors. Elliott had such
things, (or was it, Frys in phoenix?) Nevertheless, one can
get cheap ($15) SCA adapters that make this problem easier
than trying many of the alternatives, IMO. (think mail
order)

narrow SCSI drives are getting scarce due to their age, but
one can find lots of cheap SCA drives. IMHO, one can use
such a drive in a narrow 8 bit HBA application. Just
terminate it appropriately.

I used to toy with putting connectors on ribbon cables, but
often that turned out to work poorly in the long run. At
first I used pliers to squeeze the connector on to the
cable. And after that didn't work reliably, I used a smooth
jawed vice, which didn't consistently work well either. I
used to do manufacture of aircraft grade connectors and wire
harnesses, but somehow attaching connectors to 'simple
ribbon cables' was beyond me at times. (my excuse is that
brand X taiwan connector applicability isn't guaranteed with
brand Z ribbon cable)

If you are looking for a guide on using wide / narrow /
whatever kind of SCSI drive on whatever kind of host bus
adapter, I revel in the advice once found on Adaptec's
support pages.

They explained in excruciating detail the various

1. types of SCSI cables,
2.widths of SCSI buses
3. speeds and compatibility of said types.
4. how to connect and terminate any type of situation
including wide / narrow | narrow / wide matchups.
5. High voltage/ low voltage/ differential/ single ended -
dual ended / fiberchannel - detail ad nauseum.

FWIW.

I don't know the following vendor. The following is an
example.

http://www.computercablesource.com/scsi-sca-adapter-sca-80-female-to-hd-68-female-and-idc-50-male-internal-se-with-active-termination-973.html

Way too pricey, IMO but just another example. Cut
terminators off the previous example for 1/3 the cost.
http://www.computercablesource.com/scsi-sca-adapter-sca-80-female-to-idc-50-male-internal-se-with-active-high-byte-termination-976.html

----- Original Message ----- 
From: "Bexley Hall" <bexley401 at yahoo.com>
To: "Tucson Free Unix Group" <tfug at tfug.org>
Sent: Monday, August 20, 2007 5:04 PM
Subject: Re: [Tfug] SCSI disks

>
> --- John Karns <johnkarns at gmail.com> wrote:
>
>> On 8/16/07, Bexley Hall <bexley401 at yahoo.com> wrote:
>> > However, the LX uses "50 pin (SE) SCSI".  I've
>> > never seen a 50 pin drive larger than 4G (but
>> > I suspect they exist -- or existED!).  In any
>> > case, I don't *have* such a device.
>> >
>> > *But*, I can probably find a *wide* SCSI drive
>> > (non-SCA) of a larger size.
>>
>> > But, is this as "simple" as getting a cable
>> > with a 50 pin berg connector on one end and
>> > a 68 pin wide scsi connector on the other?
>>
>> Yes, I've done exactly that, connecting a 68-pin
>> wide drive to an
>> Adaptec 50-pin 1460 slim SCSI pcmcia card to read /
>> write the drive.
>
> Ah, OK.  But, how did you handle the termination on
> the drive end of the cable?  ("Termination??  *What*
> termination???  :>  )
>
>> > I have just such a beast *but* I think it was
>> > intended to go from a wide *host* to a narrow
>> > *target* (i.e., there is a terminator on the
>> > 50-pin end of the cable) -- not exactly what
>> > I was looking for.
>> >
>> > Can I cut off the terminator (on the cable)
>> > and, *if* the drive supports it, enable
>> > termination on the drive?
>>
>> I would say yes.  For me, for termination on the
>> cable, I prefer a
>> pluggable terminator anyway.  Aside: the 50 pin
>> connectors, if you can
>> find them anymore, are "instant install", in that
>> they pierce the
>> cable when pressed onto the cable, so you don't have
>> to solder each
>> connection.  This makes it practical to add a
>> connector for a
>> pluggable terminator, should you need it later on.
>
> I have lots of IDC (e.g., Berg-style) connectors.
> But, *my* problem is the cables that I have are
>
> 68W --------------- 50SE ----- terminator
>
> I.e., they are expecting the "host" to be located
> at the 68 pin end (with its on-board termination)
> then, the narrow, SE drive on the 50 pin connector.
> Finally, the terminator dangling off the end to
> terminate the *drive* end of the cable.
>
> I would cut off the terminator in my application
> since that would be the "host" end of the cable
> (and the host is already terminated).  *But*,
> there is no way to "extend" the 68 pin end to tack
> a terminator on there for the *drive* end of the
> cable!  So, I would have to count on the drive
> having termiation onboard, etc.  (I haven't looked
> into this, yet)
>
>> I found the SCSI specs are remarkably well thought
>> out regarding maintaining backward compatibility.
>
> Yes, though the standards have changed considerably
> since their SASI origins.  :<  E.g., we don't deal
> with "A" and "B" cables anymore... (thankfully)
>
>> > Grrrr.... "Standards are great; everybody should
>> > have one!"  :(
>>
>> Hey, have you been talking to the MS people?  (OOXML
>> vs ODF)  :)
>
> <grin>
>
>
>
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