AHA-2940 Ultra/Ultra Wide

[Klaus Steinberger]

Taras M. Dowhaluk wrote:
> Could we just put this down to the AHA-2940UW 'getting confused' and
> needed to be reset ? Firmware is software after all.
Maybe anything is possible.

> AHA2940UW at one end, Iomega supplied terminator at the other. Now
> I'm assuming that passive means no power to it, eg. a plug, and
> active means powered, eg. scsi-card, disk drive et al.
Active means a Terminator with a so called thevenine circuit.
It has an active circuit, it is a special very stable voltage
source with an resistor to every signal pin.

An passive terminator is just one resistor to GND and one to +5Volt
for every signal pin.

The point is that the active terminator provides an more exact and
stable termination, and is definitly required for rates of more than
5 Mbyte/sec.

Check if your IOMEGA supplied terminator is really an active one.
Probably they use a passive one as its much cheaper.

> AHA-2940UW has auto terminate. Other end is the Iomega terminator.
> Disk drives have jumpers for scsi-id only, other jumpers removed.
On some older drives, there are passive terminator as pullable resistor
arrays on the drive.

> narrow ribbon cable.
Is normally good enough, but only for internal drives!

Also be aware that some older drives do not work very well when
Ultra SCSI support is enabled on the controller. I had such 
problems before. Also with enabled Ultra very good terminators
are a must.

Sincerly,
Klaus


-- 
Klaus Steinberger               Beschleunigerlabor der TU und LMU
Muenchen
Phone: (+49 89)289 14287        Hochschulgelaende, D-85748 Garching,
Germany
FAX:   (+49 89)289 14280        EMail:
Klaus.Steinberger at Physik.Uni-Muenchen.DE
URL: http://www.bl.physik.tu-muenchen.de/~k2/