| I have just started looking at SCSI-2 docs. It looks/sounds like SCSI-2 just
defines things that the SCSI-1 spec didn't and adds some detail to thinks that
may have been open for interpretation. It is not intended to be a new and
different disk connect :-), though it does add some (compatible) extensions.
Their (the ANSI subcommittee) intent is that SCSI-1 disks will work with
SCSI-2 compliant devices (including hosts).
I'm far from an expert on SCSI, but from what I've read you should be able to
use all your SCSI-1 disks.
Ray
|
| <<< SSAG::DISK$ARCH2:[NOTES$LIBRARY]ASK_SSAG.NOTE;2 >>>
-< Ask the Storage Architecture Group >-
================================================================================
Note 974.1 SCSI-II specs required 1 of 1
STARCH::HAGERMAN "Flames to /dev/null" 34 lines 23-SEP-1991 12:53
-< SCSI-2 vs. SCSI-1 >-
--------------------------------------------------------------------------------
SCSI-2 is intended to be upward compatible with SCSI-1, and for most
purposes the two may be considered the same. From the marketing
viewpoint, the message is that we (Digital) support SCSI-2. Privately
it should be understood that the primary reason for this is their
compatibility.
Also, it should be understood that the ANSI SCSI-2 standard is
still a draft standard, and there are no devices out there that are
guaranteed to be 100% SCSI-2 compliant because the standard isn't
complete. However, after five years of work, the committee is very
close to publishing the official SCSI-2 standard and many vendors,
including Digital, claim to support SCSI-2 based on the current draft
document.
Briefly, the differences between the two are as follows.
At the physical and electrical level, SCSI-2 adds specifications for
additional connectors, an alternative termination scheme, more
details on the cable specification, and new "fast" and "wide" versions
of the bus. There are also numerous changes and fixes in the message
protocol and command definitions. For disks, the Common Command Set was
incorporated into the standard. Additional device types were created.
The SCSI-2 spec is about 500 pages long and draft versions are
available in hard copy only from Global Engineering Documents,
800-854-7179. The current draft version is 10g, although they may be a
bit behind--any version past 10c is ok except for the most exacting
purpose.
There is an electronic copy of the document that contains the text only
(no pictures or page formatting information) that may be used for
searching for specific questions. Contact me by mail if you want
access.
Doug Hagerman
|