> From: Jeff Walther <[EMAIL PROTECTED]> >> From: David Elmo <[EMAIL PROTECTED]> >>
>> ... I noticed that on one of my CD SCSIs there was a pin pair marked >> "term power" and another was "termination" Most of my other CD SCSIs had >> only "Term power" marked on one pin pair, no mention of "termination" on any >> other pin pair. What gives here? > > > In order for SCSI > termination to work properly, termination power must be present. In > general, the SCSI host (controller) supplies proper termination > power. But, in some cases inferior cables fail to pass that > termination power on to the next device and so it never reaches the > end of the chain where it is needed. Also, if more than one device > is supplying termination power to the chain, it can cause problems, > perhaps contention resulting from differences in the level settings > of the voltage regulators involved. > ... > > And then there's the fact that folks often enable termination power > thinking that it is termination, and so have too much of the one and > not enough of the other. Your CDROM drives are likely Apple models > which have no provision to supply termination. On machines shipped > with those drives there was a termination module on the end of the > SCSI cable itself. I did once get an actual telephone help person > on the line who was familiar with those drives (4X or 8X IIRC) but it > was more than six years ago and I can't remember if he told me that > there was no termination available on those drives, or if there was > an unlabeled jumper on the jumper bank that was actually termination. I want to find out which of the last 2 possibilities you mention are true. I will try to find a specific PDF on the drives concerned. The CD drive I have in my 7600 is a Matshita, Rev: XS07, Prod ID: CD-ROM CR-508 It is 12X and has always seemed to need this special Toolkit CD software driver instead of the Apple standard one. This CD works fine but I recently *unjumpered* after several years the term power (btw, termination was unjumpered as it was not on the end of any chain) as I am looking into this SCSI business. It has made no difference that I can see. So I am assuming that the 7600 is supplying the needed power and that I was right to remove it and avoid the possible "problem" of too many cooks you mention. On the Apple CDs I have lying about, there are 7 pin pairs, the first three to the left are supposed to be jumpered. The far right is labelled "TERM POWER", the others are unlabelled, maybe one of them (probably the one next to the end right) would be termination. I suppose this shows the 7600 does supply termination power on its internal scsi bus? Or does it? David Elmo -- 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:[email protected]> To unsubscribe, email: <mailto:[EMAIL PROTECTED]> For digest mode, email: <mailto:[EMAIL PROTECTED]> Subscription questions: <mailto:[EMAIL PROTECTED]> Archive:<http://www.mail-archive.com/pci-powermacs%40mail.maclaunch.com/> iPod Accessories for Less at 1-800-iPOD.COM Fast Delivery, Low Price, Good Deal www.1800ipod.com
