Help: 40mb Instead of 80mb Data Rate/"Active negation" Problem?

D

Darren Harris

Someone is testing out some LVD SCSI drives I gave him, and he told me
that the data rate with the cable I gave him is 40mb instead of the
advertised 80mb per second.

He said he thinks that some sort of "Active Negation" terminator is
needed, and I was wondering if someone could elaborate on what these
are and where I may be able to find them.(Or come up with any other
solution to overcome this problem).

The hardware involved is as follows:
1) Four Seagate 18.21 SCSI drives st118273lC.
2) Four SCA Adaptors(Ultra4 320/m SCSI compliant).
3) One Amphenol Spectra Strip.(AWM 80C 1131941 CSA AWM 1 A80C 150V FT
1).
It has a terminator, but apparently it is the incorrect one, and needs
to be changed.

Any help would be greatly appreciated.

Thanks a lot.

Darren Harris
Staten Island, New York.
 
T

Triffid

Darren said:
Someone is testing out some LVD SCSI drives I gave him, and he told me
that the data rate with the cable I gave him is 40mb instead of the
advertised 80mb per second.

He said he thinks that some sort of "Active Negation" terminator is
needed, and I was wondering if someone could elaborate on what these
are and where I may be able to find them.(Or come up with any other
solution to overcome this problem).

The hardware involved is as follows:
1) Four Seagate 18.21 SCSI drives st118273lC.
2) Four SCA Adaptors(Ultra4 320/m SCSI compliant).
3) One Amphenol Spectra Strip.(AWM 80C 1131941 CSA AWM 1 A80C 150V FT
1).
It has a terminator, but apparently it is the incorrect one, and needs
to be changed.

Any help would be greatly appreciated.

Thanks a lot.

Darren Harris
Staten Island, New York.
Click to expand...

Any markings on the terminator which might help us identify it's
specifications?
 
D

Darren Harris

Any markings on the terminator which might help us identify it's
specifications?
Click to expand...

On one side it says "ACTIVE", and on the other side it has the number
"22.30037.011".

Thanks.

Darren Harris
Staten Island, New York.
 
A

Adam Nielsen

Someone is testing out some LVD SCSI drives I gave him, and he told me
that the data rate with the cable I gave him is 40mb instead of the
advertised 80mb per second.
Click to expand...

Are you using LVD cables? Some LVD drives will work at 80MB/sec with
non-LVD cables (I have a Compaq 4GB that does) but most drives will fall
back to the fastest non-LVD speed, i.e. 40MB/sec. If the cable is LVD
compatible, it should have the correct terminator. If it's wrong, you
usually just get data errors rather than a fallback to 40MB/sec.

Also make sure the controller and/or the drive isn't set to Ultra Wide,
as you can disable LVD mode on most controllers and drives via jumpers
or BIOS settings.

Cheers,
Adam.
 
F

Folkert Rienstra

Darren Harris said:
Someone is testing out some LVD SCSI drives I gave him, and he told me
that the data rate with the cable I gave him is 40MB/s instead of the
advertised 80MB/s.

He said he thinks that some sort of "Active Negation" terminator is
needed, and I was wondering if someone could elaborate on what these
are and where I may be able to find them.(Or come up with any other
solution to overcome this problem).
Click to expand...

Although an LVD terminator is of the sort "active negation" you need
a specific LVD or LVD/SE terminator.

Terminators that say "Active" on them are SE.
 
F

Folkert Rienstra

Adam Nielsen said:
Are you using LVD cables? Some LVD drives will work at 80MB/sec with
non-LVD cables (I have a Compaq 4GB that does) but most drives will fall
back to the fastest non-LVD speed, i.e. 40MB/sec.
Click to expand...

Pure nonsense. Fallback (Domain validation) only occurs with Ultra160.
If the cable is LVD compatible, it should have the correct terminator.
Click to expand...

Or not. Not all cables come with terminators.
If it's wrong, you usually just get data errors rather than a fallback
to 40MB/sec.
Click to expand...

Nonsense. Just a moment ago you said the complete opposite.
You make things up where you stand, don't you.
Also make sure the controller and/or the drive isn't set to Ultra Wide,
as you can disable LVD mode on most controllers and drives via jumpers
Click to expand...
or BIOS settings.
Click to expand...

No you can't. But you can disable higher than 40MB/s bus transfer rates.
 
F

Folkert Rienstra

Darren Harris said:
On one side it says "ACTIVE",
Click to expand...

Then it is SE.
Get a LVD cable with LVD or LVD/SE terminator attached to it.
These are usually available cheap when coming from surplus.
 
D

Darren Harris

Folkert Rienstra said:
Then it is SE.
Get a LVD cable with LVD or LVD/SE terminator attached to it.
These are usually available cheap when coming from surplus.
Click to expand...

The ones I've found on the internet so far are expensive. Can you
recommend any sources?

And I assume that just getting a termiinator and replacing the one
already on the cable is not a good option, correct?

Thanks a lot.

Darren Harris
Staten Island, New York.
 
E

Eric Gisin

The ones I've found on the internet so far are expensive. Can you
recommend any sources?
Click to expand...
There is nothing wrong with the "new" surplus U2W cables. The ones I got were
made for HP.
And I assume that just getting a termiinator and replacing the one
already on the cable is not a good option, correct?
Click to expand...
The cable+term is probably cheaper.
 
F

Folkert Rienstra

Darren Harris said:
The ones I've found on the internet so far are expensive. Can you
recommend any sources?
Click to expand...

Punch in E124936 in Google.
Or use Compaq or HP or surplus in combination with your LVD cable search.
And I assume that just getting a termiinator and replacing the one
already on the cable is not a good option, correct?
Click to expand...

That's fine too. But you'll probably pay full price for it.
You should be able to get a terminated cable for 5-10 dollars.
I bought mine for 5 Euro at a computer fair.
 
D

Darren Harris

Eric Gisin said:
There is nothing wrong with the "new" surplus U2W cables. The ones I got were
made for HP.

The cable+term is probably cheaper.
Click to expand...

Any idea on the best place to get it?

Thanks.

Darren Harris
Staten Island, New York.
 
E

Eric Gisin

Darren Harris said:
"Eric Gisin" <[email protected]> wrote in message

Any idea on the best place to get it?
Click to expand...
Whenever you are buying technology over 5 years old the place is ebay. I'm
sure there are alternatives on the web, but it takes hours to find what you
want.
 
A

Adam Nielsen

Are you using LVD cables? Some LVD drives will work at 80MB/sec
Pure nonsense. Fallback (Domain validation) only occurs with Ultra160.
Click to expand...

Sorry yes, you're right. I was thinking of the fallback to non-LVD
speeds that occur when there's a SE drive in the chain, which is
(probably) not the case here (unless one of the drives is set forced to
SE, see my last point.)
Or not. Not all cables come with terminators.
Click to expand...

Well, obviously if it doesn't have a terminator then it doesn't have a
terminator, but if it does come with a terminator it should be the right
one.
Nonsense. Just a moment ago you said the complete opposite.
You make things up where you stand, don't you.
Click to expand...

My my, we are on the offensive today aren't we??? There's no need to
attack me just because you disagree with something I said.

A moment ago I said that most drives will fall back if using the wrong
cable, and now I said that if you're using the right cable but a dodgy
terminator you get data errors - that's not the opposite...
No you can't. But you can disable higher than 40MB/s bus transfer
rates.
Click to expand...

Well obviously LVD == higher than 40MB/s transfer rates, so whatever the
option is called it has the same effect. Likewise the jumper on the
drive is labelled "Force single ended" but it'll still effectively
disable LVD modes.

Cheers,
Adam.
 
F

Folkert Rienstra

Adam Nielsen said:
Sorry yes, you're right. I was thinking of the fallback to non-LVD
speeds that occur when there's a SE drive in the chain, which is
(probably) not the case here (unless one of the drives is set forced to
SE, see my last point.)
Click to expand...

Yes, but then NO drive will work at 80MB/sec bus transfer
as all are forced to SE mode. Same with a SE mode terminator.

If you have a substandard cable and all drives are LVD then you may get
data transfer problems with U2W. You get a lower than optimal bus trans-
fer speed -but still in LVD mode- with Ultra160 due to Domain Validation.
Well, obviously if it doesn't have a terminator then it doesn't have a
terminator,
Click to expand...

But a terminator is then added to it. This is where confusion may take place.
but if it does come with a terminator it should be the right one.
Click to expand...

If it comes with it then usually it is the right one.
My my, we are on the offensive today aren't we??? There's no need to
attack me just because you disagree with something I said.
Click to expand...

I don't disagree, you are flat false. To be so wrong on al-
most everything it is obvious that you are making it all up.
A moment ago I said that most drives will fall back if using the wrong
cable,
Click to expand...

Which was wrong.
and now I said that if you're using the right cable but a
Click to expand...
dodgy terminator
Click to expand...

You said "correct terminator".
you get data errors -
Click to expand...

Which is also wrong. A SE terminator forces fallback to SE mode.
that's not the opposite...
Click to expand...

Actually it is as you have that completely mixed up:
Wrong (substandard) cable: errors.
Wrong terminator: fallback to SE mode.

Jumpers yes, bios no.
Well obviously LVD == higher than 40MB/s transfer rates,
Click to expand...

Yes, but lower or equal than 40MB/s isn't automatically Single Ended.
so whatever the option is called it has the same effect.
Click to expand...

Nope.
LVD 40MB/s and SE 40MB/s may be the same speed but not the same mode.
Likewise the jumper on the drive is labelled "Force single ended" but it'll
still effectively disable LVD modes.
Click to expand...

Gee, maybe that is why they called it Force SE and not force 40MB/s, don't
you think?
 
D

Darren Harris

Someone should come up with a chart to keep track of all this.

Nevertheless, from what you said, it comes down to getting a cable
with a terminator that says "Active Termination". Any others probably
will not give me the 80mb per sec. data transfer rates, correct?

The part number you gave me(E124936) didn't bring up much. I need a
cable that allows for at least 4 devices. If I could get the correct
terminators for the 6 device cables I already have, I'd be set.

I'd also like to point out that a couple of previous posts in the
Google newsgroups state that the cable you mentioned(E124936) is not
LVD compatible.

I want to get a couple from Ebay, but I doubt many sellers put all of
the cable info in their ads, and knowing what I'm looking at is
difficult.(I just don't want to be stuck with more cables that are the
wrong type).

Thanks a lot.

Darren Harris
Staten Island, New York.
 
E

Eric Gisin

A search of "LVD SCSI cable" came up with perfect match:
cgi.ebay.ca/ws/eBayISAPI.dll?ViewItem&item=3496922835
 
D

Darren Harris

?!?

But "Active Negation" is nowhere in that ad.

What terms would I have to see in an ad in order to be sure thble has
"Active Negation terminators?

Thanks a lot.

Darren Harris
Staten Island, New York.
 
D

Darren Harris

Okay. I guess it's going to be a crap-shoot.

Can anyone at least tell me if there is any other possible issues
besides the SCSI cable terminator that I should be looking at that may
limit drives with an 80mb per second maximum data rate to 40mb per
second?

Thanks.

Darren Harris
Staten Island, New York.
 
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