Re: SCA SCSI drives for Ultra 1

[Chris Ross <cross+netbsd%distal.com@localhost>]

On Friday 16 January 2009 09:59:32 you wrote:
> Hi all,
>
> I'm relatively new to NetBSD, and new to the mailing list.

  Welcome!  I'll let someone who knows more about the hardware than I give you 
the full answer, but I thought I'd shoot a quick note back.

> My question is this - the Ultra 1 has an SCA SCSI backplane that can
> support two disks. I know that there are two versions of SCA, SCA-1
> and SCA-2, but it's difficult to find information about them, so I am
> unsure what version the Ultra 1 has (the service manual doesn't say,
> either), whether they are backward compatible, etc. I don't want to
> buy a 74 GB disk only to find that it doesn't work in my system.

  I must admit, I don't know the difference between SCA-1 and SCA-2.  But, 
given the age of the system, I'm sure the Ultra is SCA-1, unless what "SCA" 
used to mean is different than what "SCA-1" now does.  :-)

> I also know (from the Wikipedia article) that there are "single-
> ended" and "low voltage differential" types of SCA - http://
> en.wikipedia.org/wiki/Single_Connector_Attachment - but not sure what
> difference, if any, that makes for me.

  I'm 99% sure that's not an SCA thing, but a SCSI thing.  In either case, the 
SCSI controller in the Ultra is definitely a single-ended one.  I think most 
newer LVD drives also can do single-ended.  I'm 99% sure at least that LVD 
controllers can handle single-ended drives.

  Generally, with a machine of that age (I have a few myself), the older the 
technology is, the more likely it is to work.  (*grin*)

  Thanks.  Again, I presume a more detailed answer will be forthcoming, but I 
thought I'd offer what I could, since I have the chance.

                                           - Chris