OK Now i have a new toy - can you help me with a few things?

[xortam]

Paddy ... Your 68 pin model (which apparently is the only one with an auxiliary connector) needs to be separately terminated: at a later point on the cable, after the drives. Note under the Auxiliary connector diagram, it states that "LVD/SE Multi-mode model has no terminator". Also, note under "Jumper options" ...

Enable SCSI terminator/Force SE mode (Position #6 on J-4)


SE model
Enable SCSI terminator
If the jumper is installed, the internal SCSI active terminator on the drive works.

LVD/SE Multi-mode model
Force SE mode
If the jumper is installed, the drive is forced to work as Single-End mode drive.

UW devices normally need active termination vs. passive termination. Active terminators are much more expensive and use power from the SCSI bus to terminate the signals (the external ones normally have an LED indicating the bus is powered).

P.S. Active termination as defined on Adaptec web site:

ACTIVE TERMINATION:
An active terminator actually has one or more voltage regulators to produce the termination voltage, rather than using resistor voltage dividers.
This is a passive terminator:

TERMPWR ------/\/\/\/------+------/\/\/\/----- GND
|
|
SCSI signal

Notice that the termination voltage is varies with the voltage on the TERMPWR line. One voltage divider (two resistors) is used for each SCSIsignal.

An active terminator looks more like this (supply filter caps omitted):

+-----------+
TERMPWR ----| in out |----+-----/\/\/\/-----SCSI signal
| gnd | |
+-----------+ |
| +-----/\/\/\/-----SCSI signal
| |
GND --------------+ |
+-----/\/\/\/-----SCSI signal
|
etc.

Assuming that the TERMPWR voltage doesn't drop below the desired termination voltage (plus the regulator's minimum drop), the SCSI signals will always be terminated to the correct voltage level.

[This message has been edited by xortam (edited 18 November 2000).]

[Gurm]

Paddy,

What this means (practical upshot) is that you need to scurry out to your local Best Buy or CompUSA or whatever they have where you live, and get an active terminator. It'll run you about $30 (US). Then slap it on a connecter AFTER the drive, and you're good to go.

I hadn't realized that your drive model had no termination, otherwise we could have fixed you up right quick.

- Gurm

------------------
Listen up, you primitive screwheads! See this? This is my BOOMSTICK! Etc. etc.

[Paddy]

My dad has the same setup (adaptor, uw disk and w cdrw) however his works fine with no active termination. The only difference is that his 68pin cable has two ports on it where as mine has three.

Does that mean that his cable has a terminator on it? (if so i'll swap 'em round...)

[xortam]

The internal active terminator looks like a small PCB attached at the very end of the ribbon cable. Improperly terminated SCSI busses may or may not show up as problems depending on the devices attached and the physical location of that device on the bus; also those problems may be intermittent. Your father's system may be properly terminated of he may just be getting away with an improperly terminated bus. Don't rely on getting away with an improperly terminated bus.

I take it on your system that you've got the Plextor internal CD-RW connected to the 50-pin internal connector of your SCSI card and your IBM HD connected to the 68-pin internal connector of your SCSI card?! In this case, the auto-termination of your SCSI card (which resides in the middle of your SCSI bus) would be disabled and you need to terminate the CD-RW and your HD. The CD-RW has its own termination and you've verified that its set. The HD doesn't have termination so you need to add a active terminator to the end of its bus segment (after the drive). Just to confuse things a bit more ... normally its discouraged to add cable and terminator after the last device in a chain because it can act as an antenna and introduce noise onto the bus. I would imagine that's not a problem in this case because a) its an internal ribbon cable, and b) you'll be using an active terminator.