On Friday 04 February 2005 14:58, James D. Freels wrote:
>On Fri, 2005-02-04 at 14:36 -0500, Gene Heskett wrote:
>
>The cable IS completely disconnected from the scsi card and the
> cd-rom IS the only
>device on that cable. This is what is so strange. I did this test
>thinking it might
>fix my problem since I am down from 2-internal, 1-external on the
> same card to
>1-internal, 1-external. Both of which are terminated. The CD
> powered off should
>have little to do with the problem since it is not connected to
>anything.
>
>> The cd should be disconnected from the scsi cable entirely for
>> that test. Puyrchance is it the last device, on the last
>> connector? In which case it should have the terms turned on and
>> power applied, or some other means of terminating the cable's end
>> applied to the cable when its unplugged from the data cable.
>
>I am thinking about ordering an Lsi Logic LSIU80ALVD card ($70) and
>dedicate to this new device.
>But I am not sure if the sym53c87xx-2 linux driver will work for it
> on the alpha. It should since
>that driver works for the present card. For $70, it is worth a
> test, no ?
No? Wrong answer... Yes, certainly. And since there is no
difference in the software protocol that I'm aware of, the driver
should work, this difference you relate to us below is 100% hardware
only I believe.
>The Exabyte tech did specify an LVD card, but I think he is going
> for performance. I am just trying to
>get the thing to work at this point.
Aha, LVD! LVD is not compatible with the rest of the system unless
the rest of the system is also LVD. It is two, completely seperate
signalling methods that just happen to use the same cabling.
LVD means Low Voltage Differential. It is a 2 wire per data line
system that trades what would be the regular interfaces normal "wired
or" open collector TTL range voltages working against ground, with a
grounded wire in between each active conductor in the ribbon cable
for shielding and a shared, very low impedance ground between the
devices since about 24 of the 50 wires in the narrow cable are used
for ground.
The LVD trades the ground wire out for its use as a comparator signal,
where the signals voltages are compared to the other conductor, one
being driven a few millivolts low, and the other a few millivolts
high, or vice versa to determine if its a zero or a one. These
interfaces can be very fast, up to 320MB/second with good cabling.
I hope the exabyte has not been damaged by being plugged into a normal
high voltage single ended circuit. We have heard anecdotal stories
of damage to the LVD interface a time or 2 by such a cross
connection.
So basicly, yes, if the exabyte is an LVD device, then you must have
an LVD capable scsi card to interface with it. Unless the manul
describes a way to switch it, and since there are hardware diffs, it
would be pretty complex to do that. Its probably easier to just
change the drives interface card out for the other type of hardware.
--
Cheers, Gene
"There are four boxes to be used in defense of liberty:
soap, ballot, jury, and ammo. Please use in that order."
-Ed Howdershelt (Author)
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Yahoo.com attorneys please note, additions to this message
by Gene Heskett are:
Copyright 2005 by Maurice Eugene Heskett, all rights reserved.
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