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* Greg A. Woods <woods@weird.com> [2003-07-05 22:35:41]:
> [ On Saturday, July 5, 2003 at 19:39:52 (+0100), Matt Dainty wrote: ]
> > Subject: Re: RAIDFrame problem
> >
> > Just to rule as much out I've now replaced the cable with the shortest
> > one I have, problem with the disks being LVD is that there's no TERM
> > jumper on the disks, so I've got to use a terminated cable, and the only
> > ones I have are LVD ones about 1.5m long with about 5 connectors.
>=20
> Hang on a minute here.
>=20
> You said you have "Seagate ST39102LC disks on an Adaptec 2940UW".

Uh-huh.

> There's no way those disks are actually using LVD -- they must be
> negotiating a single-ended bus attachment since as far as I know that
> controller only supports single-ended Ultra-WIDE, and the Adaptec
> specifications confirm:
>=20
>     Electrical Drivers
>        Single-ended, active, programmable via
>        SCSISelect configuration utility

I understand the disks won't be using LVD as they're on a UW bus, but
I've never read anything that says I can't do that, without accepting
that the disks will slow down to the speed of the adapter. I also read
somewhere that due to the spec of LVD, for whatever reasons, the
termination must/should be done on the cable, hence none of the LVD
disks I own have TERM jumpers on them anywhere. That *might* be because
I seem to only have SCA disks in either caddies or with SCA->68-pin
adapters plugged in, but *they* don't have TERM jumpers either.

> You want either a full active single-ended terminator, or a "forced
> perfect termination" terminator, on the end of the bus.  You want to
> obey SE-Ultra-WIDE rules for the cabling and connectors.  You also
> probably want to make 100% certain there are no other devices on the
> same bus, especially not if they're slower or narrow.  Make sure the
> board's termination is set to "auto".

In all of this, I've been using a properly terminated cable, just
initially, this was a 1.5m long variant, which I thought would be okay
as before LVD, the maxmimum bus length is 2m? So I thought I'd still be
inside the constraints of UW.

Your comments regarding signal noise, etc. prompted me to try and use a
shorter cable, but it still retains a terminator on the end, just the
cable length is reduced by about half.

My card has both an external and internal wide channel, and an internal
narrow channel. I can use any two of the three, so I have just those two
disks on the internal wide channel, and a TLZ09 DAT on the narrow
channel, properly jumpered for termination.

I can't access the cards BIOS from the Alpha, but I know from having it
in a PC previously, it was set to 'auto'.

Cheers

Matt
--=20
"Accept anything. Then explain it your way."

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