--- Gene Heskett <gene.heskett@xxxxxxxxxxx> wrote: > On Sunday 07 August 2005 15:53, Tony Nelson wrote: > >At 3:19 PM -0400 8/7/05, Gene Heskett wrote: > >>Nice idea Claude, but can you tell us how to tell the difference > >>between the cables so that we can properly identify them? > > > >Just google on "cable select" (with the quotes) and you'll find that > > a Cable Select cable has pin 28 connected to a ground wire at one > > device connector (master) and not connected at the other (slave); > > normally this is done by punching out a little bit of wire 28 (on a > > 40 wire cable) just past the middle connector, so you'll see a > > little hole in the cable. You'd also find that, as normally a > > single device should be at the end of the cable (slave) and a > > single device should be master, so using a Cable Select cable with > > only one device is, umm, problematical. > > > >If one must use a Cable Select cable for only one device and it > > doesn't seem to work quite right at either position, I suppose one > > could just cut the cable after the middle connector, which would > > make it the end connector. Cables are cheap. > > That solution has much to recommend it in terms of signalling > integrity. As a general rule, there should <b>never</b> be any cable > beyond the last connected device, and this is particularly dangerous > in a scsi environment where as little as 3" of unterminated cable can > and will cause data error problems from the open end echo's. I've > been looking at udma100/133 cabling for years trying to figure out > just how the hell they get away with the sloppiness and still make it > work. But that sloppiness in termination also restricts the maximum > length (18" absolute max) to something thats not always reachable in > a big tower case. > > -- > Cheers, Gene 18" max? I just orded two new UDMA 66/100/133 ROUND (inclosed) cables for my system that are 24" long. They also had 36" lengths..
