Subject: Re: SCSI woes (was Re: 2nd SCSI adapter, what to get? )
To: Simon J. Gerraty <>
From: Daniel Carosone <>
List: port-i386
Date: 11/13/1995 08:03:21
> [Simon has confusing problems reassembling zen]

I have seen before, at least a couple of times, situations where
things would work with the lid off, but not with it on. In one case,
it turned out to be an ungrounded BNC ethernet. The other, I really
don't know.

If you have the time and patience, you need to test several boots in
each configuration. The idea is to determine whether the cursing,
wiggling, and dead chickens hve any effect, or whether it's a case of
some other hidden "random" influence. Touch nothing but the power
and/or reset switch, and write down the results of each test and the
configuration. This can help a lot when, after a lot of combinations
and tests, you don't think you've gotten anywhere - walk away from the
computer and look for patterns in your notes.

Some other things to consider:

 . Have you annoyed anyone with good connections to deity recently?

 . Have you tried with a different external scsi cable? You already
   discovered that the terminator seemed to matter.

 . I always figured the lid thing must be some sort of wierd grounding
   loop/shielding kind of problem. Try putting a grounding strap
   between the cases. Are the disks grounded to their respective

 . Are you overloading the powersupply?

 . In your testing of combinations, try varying the order in which you
   power up devices. And removing other non-essential-for-booting
   cards, like ethernet, extra serials, whatever.

 . If the DMA speed is the limit for one device, what happens when
   there are two devices trying to do DMA at that speed? (This
   probably wouldn't affect probing, but still)

Good Luck! You may need it.