[RndTbl] SCSI cable length
Hartmut W Sager
hwsager at marityme.net
Fri Jul 3 21:16:41 CDT 2015
Two of the most famous single-ended classic SCSI-2 host adapters of that
era, using this 50-pin dense connector, were the Adaptec AHA-2920
non-bus-mastering series and the Adaptec AHA-2940 bus-mastering series, for
PCI slot motherboards. They also sported an internal 50-pin 2-row ribbon
connector for internal SCSI drives (and a 34-pin 2-row ribbon connector for
floppy drives in the case of the AHA-2922 and AHA-2942, I think).
You could actually have both internal and external devices on the single
SCSI chain (card in the middle), as long as you disabled the terminating
resistor pack on the card itself. You then had to be especially careful in
deciding which card/device would supply the terminating resistor power. I
recall that Fujitsu hard drives were exceptionally problematic in these
I presume you (Trevor) know all about having to set each SCSI drive/device,
including the host adapter, to a unique SCSI ID, yes?
Life with SATA and USB really is more pleasant.
Hartmut W Sager - Tel +1-204-339-8331, +1-204-515-1701, +1-204-515-1700
On 3 July 2015 at 19:48, Hartmut W Sager <hwsager at marityme.net> wrote:
> > I'm a big SCSI guy, but ...
> I too am an old SCSI fan, but my interest started to wane when so many
> SCSI signalling standards and connectors began to proliferate together with
> SCSI moving totally into the high-end server realm and away from "ordinary"
> peripherals. Oh, and then there was that "termination power" headache
> (usually selected/deselected by jumpers).
> > The device has a standard dense 50-pin 2-row connector. I thought at
> first that meant for sure LVD, but now I'm thinking it just means ultra.
> It doesn't even mean "ultra", let alone HVD/LVD. That connector became
> the norm during the single-ended classic SCSI 2 generation - to my great
> chagrin, since the Centronics 50-pin connector was so much better.
> > Is there a way to know what signalling this device uses based just on
> the connector?
> No, but:
> > I checked all available interent specs, incl the original manual, for
> the device and *nothing* specifies anything other than "SCSI".
> Since the original manual (lucky you to have that!) doesn't specify
> anything other than "SCSI", it is a near certainty that this isn't LVD or
> HVD, but simply good old single-ended classic SCSI (of at least SCSI 2
> generation). It probably isn't "ultra" either, especially if it's a
> scanner or CD drive or similar slow device rather than a hard drive.
> Hartmut W Sager - Tel +1-204-339-8331, +1-204-515-1701, +1-204-515-1700
> On 3 July 2015 at 16:06, Trevor Cordes <trevor at tecnopolis.ca> wrote:
>> I have an external SCSI device that I'd like to plug in on a 10-15' cable.
>> The device has a standard dense 50-pin 2-row connector. I thought at
>> first that meant for sure LVD, but now I'm thinking it just means ultra.
>> I need LVD to get over 1.5M cable length, according to spec. LVD lets me
>> go to 12M it appears. If it's just ultra then I'm SOL, I guess.
>> Is there a way to know what signalling this device uses based just on the
>> connector? I checked all available interent specs, incl the original
>> manual, for the device and *nothing* specifies anything other than "SCSI".
>> I'm a big SCSI guy, but my memory on the subject is starting to get
>> hazy due to disuse...
>> Roundtable mailing list
>> Roundtable at muug.mb.ca
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