>From: [EMAIL PROTECTED] >Date: Mon, 28 Oct 2002 13:56:28 EST ><< I have a Seagate SCA drive (9 G) at the end of the SCSI chain, which has a >>pin-pair called TE (next to the drive ID pins). I have it *open*, >>do I need to >>"plug" it to get termination? (I lost the instructions for this drive). >>Sometimes, the drive will not mount up at boot (most of the times it will). >>I'm pretty sure it's a lack of termination. >>
>I'm pretty sure that you do. TE, stands for Termination Enable. (I'm still >not 100% clear on the difference between TE (termination Enable) and TRMPWR >(termination power) I'll figure it out one of these days. Whenever I get a >new or used drive, I go to the manufacturers web site and download the spec >sheet, installation manual, etc. Please forgive if any details are inaccurate, but this will get the gist across. Termination Enable does indeed enable termination. Termination, at it's simplest, is a resistor across each data line/Ground line pair. This damps the signals on the data lines (wires) by dumping them into Ground in a controlled manner. If you do this too early in your SCSI chain, the signal propagates no further, and devices further down the cable get no signals on the data lines. That's why Termination should be at the ends of the cable chain and no where else. If you do not have Termination at the end of the cable chain, the data signals can reflect at the end of the cable and propagate back in the direction from which they came, causing interference with following signals. So it is essential to have termination at both ends of your SCSI cable, though sometimes SCSI will operate without it. I'm a little hazy on exactly how termination power is used, but basically it's a power supply line at a regulated voltage used for termination. You should have only one device with Termination Power enabled on your SCSI chain. In almost every case, the motherboard or SCSI card supplies Termination Power, so you should not have it enabled on any of your devices. Having Termination Power enabled on multiple devices is one of the most subtle and frustrating causes of SCSI chain problems. However, some machines such as the Mac Plus and some of the PowerBooks do not provide Term Power and so a device needs to supply it on those machines. Also, some cheaply made SCSI cables do not contain the wire which is meant to carry Termination Power, and on a SCSI chain using such an inferior cable, you'd want to enable Term Power on one device after the break which the cheap cable causes. Jeff Walther -- PCI-PowerMacs is sponsored by <http://lowendmac.com/> and... Small Dog Electronics http://www.smalldog.com | Refurbished Drives | -- Sonnet & PowerLogix Upgrades - start at $169 | & CDRWs on Sale! | Support Low End Mac <http://lowendmac.com/lists/support.html> PCI-PowerMacs list info: <http://lowendmac.com/lists/pci-powermacs.shtml> --> AOL users, remove "mailto:"; Send list messages to: <mailto:pci-powermacs@;mail.maclaunch.com> To unsubscribe, email: <mailto:pci-powermacs-off@;mail.maclaunch.com> For digest mode, email: <mailto:pci-powermacs-digest@;mail.maclaunch.com> Subscription questions: <mailto:listmom@;lowendmac.com> Archive:<http://www.mail-archive.com/pci-powermacs%40mail.maclaunch.com/> Using a Mac? Free email & more at Applelinks! http://www.applelinks.com
