Correct Termination?

[sechs]

For various reasons (including that I have too much crap in my case) I'm using a 50-pin to 68-pin adapter to connect my DVD-ROM to a run-of-the-mill rounded Ultra160 cable. The problem is that, no matter how I terminate the SE bus, my Adaptec 29160 complains that it's not terminated correctly.

I thought that the correct termination would be to use the detachable LVD/SE terminator on the cable and turn off the termination by the drive. However, this does not, of course, work.

Right now, I have the drive terminating the bus and a message from the controller that the bus is not sufficiently terminated. Except for being unable to turn on bootability, the drive works. However, I'd like to be able to attach 68-pin drives to this bus in the future for diagnostic purposes; the current termination scheme isn't going to work so well.

What should the termination scheme be?

 

[P5-133XL]

The best alternative is to use a standard multi-mode ulta160 cable with terminator and then use a standard 68->50 pin adapter without termination at the DVD=Rom.

Another alternative is to use the DVD-Rom termination (which only terminates pins 1-50) and the 68->50 pin adapter must be a specialized type that terminates pins 51<->68 only (they do exist).

 

[Buck]

I'm glad P5 frequents our forum.

 

[P5-133XL]

I thought that the correct termination would be to use the detachable LVD/SE terminator on the cable and turn off the termination by the drive. However, this does not, of course, work.

My guess, as to why it does not work, is that the cable/terminator is not a multi-mode cable/terminator. LVD and SE modes actually use different impedances. Multi-mode uses an active terminator that matches the expected impeadance of the specific mode used, so that regardless of the mode the cable will be properly terminated.

 

[sechs]

After having Windows eat itself this morning, I came back, put the terminator back on the cable (it is multimode LVD/SE), and jumpered the drive to not terminate. Lo and behold it works and the controller does not complain. I have no idea why it didn't before, but I did swear at the drive before powering the computer on.

After I get Windows in a working state, I'll see if I can figure why I can't make the drive bootable....