On Tue, 20 Mar 2001, Brian Hechinger wrote:

> Johnny Billquist drunkenly mumbled...
> > 
> > Problem isn't building a SCSI controller, but the fact that you want it to
> > look like an MSCP controller from the computer perspective.
> 
> how does this complicate things?  i mean, are we talking major complications
> or minor ones?  if i could get all the specs for SCSI, QBus and MSCP would an
> electronics genius (i view him as such) have a chance at creating such a beast?

Major complications. It's not just an issue of mapping MSCP to SCSI at an
electrical level. MSCP is a very complicated protocol, which will require
a microprocessor and some serious software to implement.
MSCP handles automatic bad-block revectoring, and helps with the remapping
of bad blocks (but the OS is also involved in that process), it has a
fairly intelligent diagnostics protocol as well, and totally hides the
physical characteristics of the drive.
SCSI is somewhat nicer to use as the physical connection than IDE
though. :-)

> > Having it talk raw SCSI isn't a good option. No boot programs exist, and
> > you'd also have problems booting it even if you did write you own boot
> > proms.
> 
> hmm, well if it were simple it would have been done already. :)

Yup.

> so:
> 
> drive <- SCSI -> MSCP <- QBus -> VAX
> 
> does that look like what we would need?

Yes.

	Johnny

Johnny Billquist                  || "I'm on a bus
                                  ||  on a psychedelic trip
email: bqt@update.uu.se           ||  Reading murder books
pdp is alive!                     ||  tryin' to stay hip" - B. Idol