At 10:12 PM 3/10/00 -0500, Lord Isildur wrote:
>no, DSSI disks should be treated liek any other MSCP disks, and use the
>ra device names. DSSI disks can be thought of as a self contained unit
>with its own HSC and a single disk attached to that HSC. thats why DEC
>called them 'independent storage elements'. The DSSI protocol is actually
>a subest of CI, as evidenced further by such things as the SHAC chip
>being used for the DSSI stuff on some machines. SHAC is a single-chip CI
>adapter. In any case the language spoken over this CI is MSCP.
>
>Isildur

I'm going to have to disagree with you a bit here. The DSSI bus is a 
separate bus just as the SCSI bus is a separate bus. Consider for a moment 
that existing SCSI disks on the VS3100 series appear as "sd0 ... sdn" and 
"attach" to scsibus0, scsibus1, etc. MSCP disks on the other hand attach to 
the mscpbus and are labels ra0, ra1, etc. Now there are DSSI disks that 
connect to the MSCP bus using the KFQSA, but that is no different than SCSI 
disks that attach to the MSCP bus through a SCSI to MSCP adapter.

So as an I/O bus, the DSSI bus on the KA640 is a separate bus just like 
SCSI, therefore I plan to treat it like SCSI and give it its own config 
lines. (think along the lines of:

dssibus*   at sii?
dd*        at dssibus? target?
dt*        at dssibus? target?

For now I've added a KA640 CPU type that will control the enabling of this 
code.

Now, as for your assertion that DSSI protocol is a subset of CI, I can't 
say that I know enough to understand that statement as made. The KA640 does 
_not_ use the SHAC chip like the KA660 and KA670 does, instead it uses 
something called the SII chip in the docs. (the KA670 docs call the SHAC 
chip the SHAC chip.:-) And in the KA670 docs the SHAC chip is identified as 
being able to operate both a CI bus _and_ a DSSI bus, although they aren't 
shown or discussed as proper (or even improper) subsets of each other.

Further, while the KFQSA appears to treat each DSSI disk as a single 
virtual controller, the SII chip on the KA640 is more like SCSI that can 
talk to several targets through a single controller.

And this statement
 > In any case the language spoken over this CI is MSCP.

Is fairly bold and spicy but I can't find any indication that it is true in 
either manual. Both refer to DSSI as having its own set of opcodes with 
targets, arbitration phases, data phases and such like, (very SCSI like) 
and neither mention anything or reference MSCP anywhere (except in the 
discussion of Q-bus peripherals)

I guess what I'm saying is that I don't intend any disrespect but I can't 
reconcile these statements with the documentation. There must be something 
I'm missing here.

--Chuck