werner@milano.sw.mcc.com (Werner Uhrig) (03/11/90)
In article <160700094@primerd> barry@primerd.prime.com writes: > > [ Barry reports that he has problems when trying to boot with the > powered off Maxtor in the SCSI daisy chain off his Mac SE...] your report is interesting as I experience similar problems in a very similar setup; to wit: SE with 4meg, running OS-6.0.4, internal Quantum-105S at address "0", 6+3 feet SCSI-cables to a Motorola tower containing a Newbury 4380S at address "1" and a Maxtor 4380S at address "4" at the end of the chain with onboard terminators and jumpers set to "internal power to terminators" AND "provide terminator power to bus" - the latter because I assume that it will allow external power to reach MAXTOR's terminators when it is not powered up. I use the LARGE drives just like Barry: power off when not needing them, SilverLining partitioned, SCSI-Tools CDEV to mount them on the fly, etc ... when the SE hangs and I have to reboot, I *HAD* to disconnect the external drives from the SCSI-bus (I do not recall if that was only true when I did not wait at least 5 minutes - but I will test that "soon" ...:-) until I decided to experiment further: I also have a TEAC-150meg tape drive, which I daisied after the Maxtor (and the TEAC also has onboard terminators, which did not seem to matter at all), and which I also like to keep powered off most of the time ... On an impulse, I added one of those external terminators from Apple into the cable just before the TEAC - and I have had no rebooting problems since, no matter which drives are on or off. I've tried several times to find someone (or some pointer to a write-up) to get the definite poop on terminators and related hardware concepts - but "no joy" so far.... >after the "smilely Mac" screen. In a reboot after turning off the Maxtor, >the "smilely Mac" screen often displays for 10-20 seconds, during which >time there is heavy activity on the internal hard drive. same here. One item I suspected but have since discarded was the theory that the "StartUp Device" might point to the Maxtor but not so; another theory was some INIT on drive 0 that is trying to mount a partition on the Maxtor, given that it "sees" it's address on the chain ?!? but I discarded that one also! >I've tried doing a shutdown after powering down the Maxtor followed by a >power off/on sequence on the SE. This only works if I let the Mac sit >with the power off for more than about 5 minutes (could there be a >capacitor that has to discharge?). if you have either no or a rundown battery, it takes about 5+ minutes for the PRAM-values to reset to default-settings (boot from drive 0, I believe, and 0 is normally the SE-internal drive, unless you changed some jumpers) - but I do not really suspect that to be the problem. I DO suspect that you (also) have the jumpers set on your Maxtor embedded SCSI-control circuits to power the bus, and there might be some caps there that take 5 minutes to discharge (with side-effects unknown to me) > The only other _sure_ cure seems to be >shutdown the Mac, turn off Mac power, disconnect the SCSI cable from the >SE, power on (this results in a normal boot), shutdown, power off, >reconnect the cable, power on. same here. hmm, maybe when the SE's circuits see "someone else" on the bus trying to power the terminators on the bus, it stops trying to power the bus herself and looses the internal hard drive somehow ... gee, I better stop speculating and go find a real hardware guru - I know we have some around here somewhere ... :-) btw and on the other hand, this fits what happens when the StartUp Device cannot be "seen" at boot time - boot is attempted from other drives. >I thought that there might be an issue with powering the terminator, so I >brought home the internally terminated Syquest drive I use at work and >changed the hookup to be SE <-> Maxtor <-> Syquest. In order for this >configuration to work, the Syquest drive has to be powered on. there seems to be a pattern here, doesn't there. Syquest, just like my TEAC, seems to require internal power to the terminators. > When I retried the Maxtor startup & shutdown sequences described above, > I got the same type of SE hang when I did a restart/shutdown and the same >remedies were effective. This would seem to rule out powering of the >terminator as a factor. well, not really, as my "successful remedy" might indicate (I still don't understand the electric principles of why it is working). Try what I did (hook one of Apple's external terminators into the cable just before the Syquest) and tell me/us what happens... It might require that you believe in miracles, btw, else it might not work .... :-) >The really funny thing is that I'm pretty sure (can't be positive) that >when I first started using the Maxtor in early January I was able to >reboot normally after turning off the Maxtor. I'm looking for help in >figuring out what might be causing the hang and what might have changed >since January. Why is turning off power on the Mac for less than 5 minutes >not effective whereas disconnecting the cable is? hmm, Barry, played with the jumpers in any of your hardware lately? yours in speculating (when it comes to hardware) Cheers, ---Werner PS: I am cross-posting this article to comp.sys.mac.hardware (where the original should have gone to) and the newly founded comp.periphs.scsi (where I hope to find some light for my darkness of electric ignorance) -- --------------------------> please send REPLIES to <------------------------ INTERNET: werner@cs.utexas.edu or: werner@rascal.ics.utexas.edu (Internet # 128.83.144.1) UUCP: ...<well-connected-site>!cs.utexas.edu!werner