Re: Bug#485961: installation-reports: Installer can't locate CD-ROM drive (sparc)

[Mark Morgan Lloyd <markMLl.debian-sparc@telemetry.co.uk>]

Mark Morgan Lloyd wrote:
> > [1] http://bugs.debian.org/485961
>
> 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]