Dave wrote:

> Triffid wrote:
>
>>> Thanks for that.
>>>
>>> I checked and found the disk was already jumped SE. I removed the
>>> jumper (what else to try?) but no luck. I tried a few other jumpers,
>>> but no improvement.
>>>
>>> What was odd though is that
>>>
>>> a) The disk is seen if it is the *only* disk in the machine.
>>>
>>> b) The disk is seen if it the lower slot (SCSI ID=3), but not if its
>>> in the upper one (ID=1). And no, there are not any jumpers installed
>>> on any of the SCSI ID select pins.
>>>
>>> Anyway, it is at least semi-resolved. I've put an operating system on
>>> it and it boots OK now. Just needs to be in the lower slot, otherwise
>>> it can't be seen on the bus.
>>
>>
>>
>> That's rather odd. There is no physical or logical difference between
>> the upper and lower drive bays aside from SCSI ID AFAIK.
>
>
> Yes, I thought it odd too.
>
>> I suspect your upper bay is b0rked somehow, and won't work with any
>> disk as a result.
>
>
> That is not so.
>
> Here you can see the Compaq disk that presents me trouble in the lower
> slot (ID=3) and a Seagate one in the top one (ID=1)
>
>
> ok probe-scsi
> Target 1
> Unit 0 Disk SEAGATE ST39103LC 0001LS482885
> Copyright (c) 1999 Seagate
> All rights reserved
> Target 3
> Unit 0 Disk COMPAQ HB00931931 03F168224A01GAGSPCQ3F1
> 09RI9904200012259H7007
> E32284 Q59H6952B09E31916 1999
> ok
>
>
> After I swap the disks around, using the same machine, the Compaq one
> can no longer be seen.
>
> ok probe-scsi
> Target 3
> Unit 0 Disk SEAGATE ST39103LC 0001LS482885
> Copyright (c) 1999 Seagate
> All rights reserved
> ok
>
>
> That behaviour is repeatable.
>
> But when I move the disks to another SS20, both can be seen in any
> position, but I'm pretty sure they had the same problem in yet another
> SS20.

Aha!

Is there a difference in OBP version between these two SS20s? Are the
SCSI controllers the same?

>> I have a couple of spare SS20 backplane & cable assemblies here
>> (Toronto, Canada), perhaps you could try one if the logistics aren't
>> too complicated.
>
>
> Thanks, but I am in the UK, so a long way from you, but in any case I
> have five SS20's here.
>
>> Triffid
>
>
>
> It all seems very odd. But I have had problems with other Compaq disks
> in SS20's before, so this is not a total surprise to me.
>