Mac + reads but wont' boot HD

Mac + reads but wont' boot HD

Post by Al Rich » Wed, 23 Sep 1992 21:08:02



 Greetings!

 I've recently acquired a Mac + to add to my stable of machines, and
am having a problem I've never seen before on a Mac.

 Upon connecting a Quantum 105S hard disk and formatting it with the
proper bits of software, I find I can mount, run programs from,
and use the disk easily. Even after reinstalling 6.0.5 3 separate
times, I cannot get it to cold boot upon power-up.

 The activity light on the disk blinks madly, making me suspect that
the Mac + isn't seeing drive ready quite properly. Any suggestions
as to things I might try would be appreciated.

 Yes, I zapped the PRAM.

                                                ajr

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Mac + reads but wont' boot HD

Post by Paul A. La » Wed, 23 Sep 1992 22:46:01



Quote:> Greetings!
> I've recently acquired a Mac + to add to my stable of machines, and
>am having a problem I've never seen before on a Mac.
> Upon connecting a Quantum 105S hard disk and formatting it with the
>proper bits of software, I find I can mount, run programs from,
>and use the disk easily. Even after reinstalling 6.0.5 3 separate
>times, I cannot get it to cold boot upon power-up.

Try turning on the drive and waiting until it spins up before turning on the
plus. My recollection (from friends who had Plus's) is that the disk has to
be on before the Mac.
Quote:> The activity light on the disk blinks madly, making me suspect that
>the Mac + isn't seeing drive ready quite properly. Any suggestions
>as to things I might try would be appreciated.


 
 
 

Mac + reads but wont' boot HD

Post by Dave Pla » Sat, 26 Sep 1992 03:19:07


Quote:> Upon connecting a Quantum 105S hard disk and formatting it with the
>proper bits of software, I find I can mount, run programs from,
>and use the disk easily. Even after reinstalling 6.0.5 3 separate
>times, I cannot get it to cold boot upon power-up.

> The activity light on the disk blinks madly, making me suspect that
>the Mac + isn't seeing drive ready quite properly. Any suggestions
>as to things I might try would be appreciated.

There are two quirks in the Mac Plus SCSI interface which may affect the
machine's ability to boot from certain hard disks.

The older (beige) Mac Plus systems will reset the SCSI bus frequently
when they look for a drive to boot from.  The machine polls each address
on the bus;  if it doesn't find a drive which is "ready", it issues a
bus reset and then searches again, and so forth.  Most SCSI disk drives
will respond to a bus-reset by clearing their internal state and going
through their normal self-test procedure... which can require a second
or more to complete.  If the drive takes longer to run its self-test
than the Mac Plus takes to scan the bus and reset it again, then the
drive will _never_ be ready in time for the Plus to see it and boot from
it.

This problem was corrected in later (platinum) versions of the Mac Plus.
The workaround, for beige Plus systems, is to open up the SCSI hard-disk
cabinet, remove the ribbon cable, and clip the wire which carries the
"reset" signal.  This will prevent the drive from being reset by the
Plus, and will allow the disk to boot properly.

The other quirk is that the Mac Plus (and some other Macs) are unable to
boot from drives which go into the "UNIT ATTENTION" condition when they
are powered up or reset.  This is a fairly common behavior among SCSI
hard disks.  With some models of hard disk, it is possible to disable
UNIT ATTENTION by setting a bit in one of the SCSI "mode sense" pages;
with other drives, it is necessary to replace the firmware PROM with a
different one.

--
Dave Platt                                                VOICE: (415) 813-8917

 USNAIL: New Technologies Group Inc. 2468 Embarcardero Way, Palo Alto CA 94303

 
 
 

Mac + reads but wont' boot HD

Post by Ed Sega » Mon, 28 Sep 1992 06:47:51



>  Upon connecting a Quantum 105S hard disk and formatting it with the
> proper bits of software, I find I can mount, run programs from,
> and use the disk easily. Even after reinstalling 6.0.5 3 separate
> times, I cannot get it to cold boot upon power-up.

>  The activity light on the disk blinks madly, making me suspect that
> the Mac + isn't seeing drive ready quite properly. Any suggestions
> as to things I might try would be appreciated.

Is this an APS drive (or are you using an APS HD driver), by any
chance?  For some time now, people have sporadically reported problems
booting Mac Pluses from APS drives, although APS has vehemently denied
any incompatibility problems.  However, in their latest software
release, they state that they have recently discovered a bug, and
provided a workaround.  

This bug only crops up if there is more than one device connected to
the SCSI chain (not counting the mac motherboard).  If the boot device
does not have the highest SCSI ID, then booting will not work.  To
fix, change the IDs so that the boot device has the highest ID in the
chain.  

--Ed
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