Re: Bug#485961: installation-reports: Installer can't locate CD-ROM drive (sparc)
Mark Morgan Lloyd wrote:
Two questions that might possibly help. The first is that I suspect that
the internal SCSI bus termination isn't particularly robust, I think
that putting an external (68-pin, SE) terminator on the external SCSI
connector improves reliability of hardware detection and subsequent
driver load from initrd. So:
* Is the kernel doing something which affects the electrical interface,
e.g. glitching auto-termination state during initialisation?
The second thing is that Splackware (Bobware 10.2) is much more reliable
at detecting disc drives on the internal bus than Debian (Etch, 4.0).
One particular failure mode I see with Debian and at least some disk
types is that when it scans for the CD-ROM drive it does /something/
which causes the hard disc to appear at multiple SCSI IDs including the
one that the CD is at- which obviously screws things totally. So:
* Is the installer doing something which affects the electrical
interface, e.g. a badly-implemented SCAM probe?
I've managed to duplicate some of these problems on another system,
specifically an Ultra-1. I'm fairly sure it's related in some way to
termination, and it appears to be crucially sensitive to the make and
model of disc.
I found that a pair of drives supplied with an E4500 were invisible to
the Debian "Etch" installation CD in a U1, these were IBM and Fujitsu
OEM rebranded as Sun 9G and were visible to Slackware. Using Seagates
(OEM, actually branded Compaq) I was able to install Debian, but they
still weren't reliable in the E4500.
In all cases Slackware is more reliable, but there's also a possibility
that there's some OpenPROM command that preconditions the internal SCSI
bus to handle discs that would otherwise be ignored or that would cause
repeated bus resets.
Mark Morgan Lloyd
markMLl .AT. telemetry.co .DOT. uk
[Opinions above are the author's, not those of his employers or colleagues]