Contents of DEC 8" floppies

Johnny Billquist bqt at
Fri Oct 16 05:37:33 CDT 2015

On 2015-10-16 10:08, Dave Wade wrote:
>> -----Original Message-----
>> From: cctalk [mailto:cctalk-bounces at] On Behalf Of Johnny
>> Billquist
>> Sent: 16 October 2015 09:07
>> To: cctalk at
>> 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 those
>> 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. Not 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 
DECnet stack.


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