Long messages are okay, as long as they are saying something
interesting...

On Tue, 27 Feb 2001, Michael Kukat wrote:

> Hi !
> 
> On Tue, 27 Feb 2001, BrownM03 wrote:
> > 1. Michael
> > > BTW: If you are new to VAXen... don't confuse SCSI and DSSI on you 100, or
> > you
> > > could trash this fantastic machine... It's a quite nice beast in
> > performance!
> > OK, what is the difference between DSSI & SCSI connectors?
> 
> Ehm, internally none, they just look the same. That's the reason for my
> warnung :)

Depends on what you mean by "internally". All disks works after the same
basic principles, but the interfaces to the differ a lot.
SCSI and DSSI are different interfaces, which have more or less the same
physical connectors... That is unfortunate, since you might be unhappy if
you hook the wrong controller to the wrong disk.

> > Or am I grabbing at straws there?
> > Fantastic? (I would agree ... but probably mostly from ignorance), what
> > makes this
> > box so good? I've not been able to find much documentation on it.
> 
> a) It's A VAX!

Correct.

> b) It's no Intel :)

Correct.

> c) It's the godfather of CISC-architecture

Eh? Not by a long shot. It's the mother of all CISCs perhaps, being one of
the most gargantuan CISCs around, but it's actually a development of the
PDP-11. (See next item).

> d) It's the first CPU knowing of virtual memory (i think), that's where the
>    name comes from: Virtual Address eXtension.

No way. VAX stands for Virtual Address eXtension, that much is
correct. However, the name was in reference to the PDP-11, from which it
was developed. The PDP-11 is a 16-bit architecture, and DEC found out that
the machine, while highly successful, fell short on memory. So it was
extended into a 32-bit machine. In addition to just adding 16 bits, they
also shortened the page from 8K to 512 bytes, and made the MMU a two level
thingy, in order to better handle virtual memory. The PDP-11 handles
virtual memory just fine as well, as do most older machines, as long as
they have an MMU.

Oh, and until shortly before announcing the first VAX (called VAX-11/780),
the machine was actually called PDP-11/780.

And it's true that the VAXen often are more balanced machines than your
average PC. So you can load them in ways a PC won't appreciate.
Hanging off several hundreds of terminals, printers, comm. options, and
god knows what else is/was pretty common on VAXen.

	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