lindhurs@schaefer.math.wisc.edu (Scott Lindhurst) (03/27/91)
I just connected two hard drives to my Mac Plus, and now I can't boot from one until they are both turned on. Then the one with the higher SCSI id boots. Either one connected individually will boot, it's just that when both are connected, they both have to be turned on get the Mac even to recognize their existences. Both drives are internally terminated, and my Mac Plus has the revision two (Lonely Heifer) ROMs, so according to all the documentation I can find (Tech notes, in particular), all should be well. But it isn't, and I don't want to use both drives all the time (one is old, slow, and noisy). Thanks for any help you can give me! Scott Lindhurst lindhurs@math.wisc.edu
hamilton@kickapoo.cs.iastate.edu (Jon Hamilton) (03/28/91)
lindhurs@schaefer.math.wisc.edu (Scott Lindhurst) writes: >I just connected two hard drives to my Mac Plus, and now I can't >boot from one until they are both turned on. Then the one with >the higher SCSI id boots. Either one connected individually >will boot, it's just that when both are connected, they both >have to be turned on get the Mac even to recognize their >existences. Some drives don't provide terminator power when they're switched off (they're supposed to, but...), and this has the effect of making you switch the drive on to make any drive work. I find it annoying myself, but it's one of those things you kinda have to deal with. [...] >Thanks for any help you can give me! >Scott Lindhurst >lindhurs@math.wisc.edu -- Jon Hamilton hamilton@kickapoo.cs.iastate.edu " I feel a lot more like I do now that I did before I got here " - can't remember who
pat@magnus.ircc.ohio-state.edu (Patrick E Plaisted) (03/28/91)
In article <1991Mar27.050325.3851@schaefer.math.wisc.edu> lindhurs@schaefer.UUCP (Scott Lindhurst) writes: >I just connected two hard drives to my Mac Plus, and now I can't >boot from one until they are both turned on. Then the one with >the higher SCSI id boots. Either one connected individually >will boot, it's just that when both are connected, they both >have to be turned on get the Mac even to recognize their >existences. The problem is that one of your drives (almost certainly the old one) needs to be powered up in order to provide power to the termination resistors. Even if it's not the last one in the chain, it makes your scsi chain invalid unless it's powered up, hence the reason your mac won't boot. =========================================================================== Patrick Plaisted |pat@agvax2.ag.ohio-state.edu System Programmer | or if you want to Ohio Cooperative Extension Service | torture me with unix: The Ohio State University |pat@hpuxa.ircc.ohio-state.edu 2120 Fyffe Rd. Room #109 | Columbus, Ohio 43210 | (614) 292-4338 =========================================================================== I'm not quite sure who's ideas these are; I think they're mine...
jcav@quads.uchicago.edu (john cavallino) (03/28/91)
In article <1991Mar28.110621.216@otago.ac.nz> stanger@otago.ac.nz (Nigel Stanger) writes: >In article <1991Mar27.050325.3851@schaefer.math.wisc.edu>, lindhurs@schaefer.math.wisc.edu (Scott Lindhurst) writes: [deletes speculation about why a Mac Plus wouldn't boot if both external SCSI were not powered on] More speculation, but very, very early Mac Pluses (first months of 1986) had a ROM bug that caused them to fail to boot if any SCSI devices were connected but not powered on. Does the Mac Plus in question fall into this catagory? Just checking. -- John Cavallino | EMail: jcav@midway.uchicago.edu University of Chicago Hospitals | USMail: 5841 S. Maryland Ave, Box 145 Office of Facilities Management | Chicago, IL 60637 "Opinions, my boy. Just opinions" | Telephone: 312-702-6900
stanger@otago.ac.nz (Nigel Stanger) (03/28/91)
In article <1991Mar27.050325.3851@schaefer.math.wisc.edu>, lindhurs@schaefer.math.wisc.edu (Scott Lindhurst) writes: > I just connected two hard drives to my Mac Plus, and now I can't > boot from one until they are both turned on. Then the one with > the higher SCSI id boots. Either one connected individually > will boot, it's just that when both are connected, they both > have to be turned on get the Mac even to recognize their > existences. I seem to remember something about this... Don't you have to turn on everything in the SCSI chain for it to work? Or is that only to use the device at the end of the chain?? Or am I just imagining things??? :-) > Both drives are internally terminated, and my Mac Plus has the ???!!! What?? That doesn't sound right! *Both* are terminated? Actually, come to think of it, it depends on where the SCSI chain begins and ends. Does it start at the Mac, or does it start at the first device? If it starts at the Mac, then you should get the termination removed from the first drive in the chain. Disclaimer: I am not a hardware expert, so don't take this as gospel :-) -- See ya Nigel. /******************************************************************************\ * "If I had a quote, I'd be wearing it." * Internet: stanger@otago.ac.nz * * -- Dylan Thomas (I think) * SnailMail: Information Science, * * * University of Otago, * * "Say no MORE!!!" * P.O. Box 56, * * -- Eric Idle * Dunedin, NEW ZEALAND. * \******************************************************************************/
lindhurs@schaefer.math.wisc.edu (Scott Lindhurst) (03/29/91)
In article <1991Mar27.050325.3851@schaefer.math.wisc.edu> I write >I just connected two hard drives to my Mac Plus, and now I can't >boot from one until they are both turned on. From the responses so far, I think that the answer in my case is probably that the SCSI specifications say that all SCSI devices must be powered up for everything to work; older devices may do things that require them to be on (such as not providing termination or clamping lines to ground when they are off), but newer devices are usually friendlier and the SCSI bus will work with them on or off. The only real solutions seem to be to disconnect the older drive when I'm not using it or maybe use an external terminator instead of the internal. If anyone is interested in the detailed responses, let me know and I'll send a copy. Scott Lindhurst lindhurs@math.wisc.edu
angelini@apollo.HP.COM (Bob Angelini) (03/29/91)
>I just connected two hard drives to my Mac Plus, and now I can't >boot from one until they are both turned on. Then the one with >the higher SCSI id boots. Either one connected individually >will boot, it's just that when both are connected, they both >have to be turned on get the Mac even to recognize their >existences. To begin with only the drive at the physical end of the cable should be terminated not both. If this doesn't fix the problem it may just be that the unpowered drive is loading down the bus so that the other drive isn't seen. As for the higher ID booting, thats because the higher ID has priority over the lower. Bob
hamilton@kickapoo.cs.iastate.edu (Jon Hamilton) (03/30/91)
angelini@apollo.HP.COM (Bob Angelini) writes: >>I just connected two hard drives to my Mac Plus, and now I can't >>boot from one until they are both turned on. Then the one with >>the higher SCSI id boots. Either one connected individually >>will boot, it's just that when both are connected, they both >>have to be turned on get the Mac even to recognize their >>existences. >To begin with only the drive at the physical end of the cable should be terminated >not both. If this doesn't fix the problem it may just be that the unpowered drive NO NO NO! If there are only two drives in the chain, they are _both_ supposed to be terminated. Some people claim to have luck with SCSI chains which are not 'properly' terminated, but you should really try to stick with the way things are supposed to be if at all possible - I can almost guarantee it'll save you headaches some day. Please check into things before you post. >is loading down the bus so that the other drive isn't seen. As for the higher ID >booting, thats because the higher ID has priority over the lower. >Bob -- Jon Hamilton hamilton@kickapoo.cs.iastate.edu " I feel a lot more like I do now that I did before I got here " - can't remember who