Wide SCSI-2 required two cables to do 16 bit wide transfers. SCSI-3 defined a single cable, single REQ/ACK 16 bit wide transfer. The reason you are hearing 16-bit single cable being called SCSI-3 is that they CAN. The fact that single cable 16-bit has been around for a while just shows you how much the standardization process lags behind the real world. SCSI-3 is really a family of standards. SCSI was broken up from a single document into different layers and command sets. This was done to allow for different physical transport layers (like fibre channel and SSA) to be defined, and to allow for smaller "bite-sized" projects that maybe get done a little faster.

The family includes the following members with TLAs:
- SCSI-3 Parallel Interface (SPI): Defines the mechanical, timing, phases, and electrical parameters of the parallel cable we all know and love. Some of the electrical and cable parameters are tightened/improved over SCSI-2.
- SCSI-3 Interlock Protocol (SIP): Defines the messages and how the phases are invoked. No real change from SCSI-2, except for some new messages.
- SCSI-3 Architectural Model (SAM): In a nutshell, defines a common set of functions and services and definitions for how a physical transport properly gets commands, data, and status exchanged between two devices, complete with error handling and queuing.
- SCSI-3 Primary Commands (SPC): All of the commands executed by any and all SCSI devices, like REQUEST SENSE and INQUIRY, etc.
- SCSI-3 Block Commands (SBC): Disk commands.
- SCSI-3 Stream Commands (SBC): Tape commands.
- SCSI-3 Controller Commands (SCC): RAID box commands.
- SCSI-3 Multimedia Commands (MMC): For CDROMS etc.
- SCSI-3 Fibre Channel Protocol (FCP): SCSI commands over gigabit Fibre Channel.
- SCSI-3 Serial Bus Protocol (SBP): SCSI commands over IEEE 1394 High Speed Serial Bus (Apple's "FireWire").
- SCSI-3 Serial Storage Protocol (SSP): SCSI commands over SSA.

After perusing the latest issue of Computer Shopper, I came away with the impression that companies are calling F&W scsi-2 hd's SCSI-3. Is this an incorrect assumption, or is F&W SCSI-2 known as SCSI-3? Is this really mostly marketing hype? Actually, there is something to that. TECHNICALLY, what is out there is often a hybrid: SCSI-3 "SPI" silicon with some other hodgepodge of SCSI-3 proposals, all mixed in with SCSI-2 stuff. An earlier posting said that the Quantum Empire ("SCSI-3") drives contain some commands from the SCSI-3 command set, and Adaptec suggested a specific setting on its 2940W controller to work properly with the drive.

I understand there are some drives with proposed SCSI-3 command features. These are mostly in the MODE SELECT and in error codes, as I recall. Perhaps someone who knows more about this could elaborate? Note also that the major players (like DC Drives) don't have any "SCSI-3" stuff advertised; only JDR and some cheap clones are promoting it. Besides, Wide SCSI-2 has yet to really catch on (mostly because only a few drives are fast enough to take advantage of it).

There is no "wide SCSI-2" because that would mean two cables. Single cable wide SCSI has always been SCSI-3, it just took too long to get into a standard!