Contents of DEC 8" floppies
dave.g4ugm at gmail.com
Fri Oct 16 06:00:43 CDT 2015
> -----Original Message-----
> From: cctalk [mailto:cctalk-bounces at classiccmp.org] On Behalf Of Johnny
> Sent: 16 October 2015 11:38
> To: cctalk at classiccmp.org
> Subject: Re: Contents of DEC 8" floppies
> On 2015-10-16 10:08, Dave Wade wrote:
> >> -----Original Message-----
> >> From: cctalk [mailto:cctalk-bounces at classiccmp.org] On Behalf Of
> >> Johnny Billquist
> >> Sent: 16 October 2015 09:07
> >> To: cctalk at classiccmp.org
> >> Subject: Re: Contents of DEC 8" floppies
> >> On 2015-10-16 08:14, Mark J. Blair wrote:
> >>> I have some unused 3M blank preformatted RX02 diskettes. Would
> >> be usable in an RX01 drive?
> >> Yes. The RX01 and RX02 is the same format. It's only the data part of
> >> the sector that differs.
> >>> I don't know what the VAX PSI software is, but I'm guessing it must
> >>> be
> > for
> >> the 11/780 based on the media type. I have zero use for it, but the
> > thought
> >> of 11/780 bits being returned to the entropy pool disturbs me a bit.
> >> :)
> > Can
> >> anybody fill me in on what these disks likely contain, to help me
> >> decide whether I might like to trade blank floppies for them?
> >> Yes, most likely a distribution intended for people with an 11/78x.
> >> The software was probably available on several different media.
> >> PSI is (as others have mentioned) the packetswitch interface software.
> >> So X.25 for DECnet.
> > From what I remember it does not need DECnet....
> You might be right. I partly based that comment on the RSX P.S.I product.
> sure how you'd handle this without DECnet, but I obviously don't the know
> any VMS specifics. In RSX, you can certainly communicate over X.25 without
> the DECnet overhead, but you use NCP to configure your
> X.25 links. So you need at least the CEX subsystem, but not the full
>From what I remember VAX PSI has its own programs to configure the X.25
Certainly in the early days the only connectivity that was supported was
X.3, X.28 and X.29 terminal access.
So there was an X.29 terminal program, and you could connect to the VAX from
an X.29 PAD.
The problem was as the VAX kind of insists on sending one character per
packet the overhead was horrendous.
In the UK we had coloured book protocols that ran on top of X.25 to provide
mail and file transfer.
I think Reading University wrote the VAX version but Digital marketed it.
The poor performance due to the character mode terminals and other aspects
of the software meant it was pretty much universally hated by DEC lovers as
this tirade shows...
In fact DEC had little option. If they had not provided the X.25 software
they would have been unable to sell large machines to UK Universities as
support of Janet was required to get central government funding.
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