[TUHS] PDP-11 questions

Johnny Billquist bqt at update.uu.se
Tue Jan 26 02:17:23 AEST 2016

On 2016-01-25 17:00, John Cowan wrote:
> Johnny Billquist scripsit:
>> the desktop models are called MS800A, MS800B, MS880A and MS880B.
> Good to know.

I should try and locate whatever document I have that says DECstation as 
well. Fun, if nothing else.

>> Reading through it, it's very clear that this is not OS/8, or any
>> derivative of it.
> You're right.  What it did share, however, was the OS/8 file system,
> except that the date epoch was 1972 instead of 1970.  I don't know if
> COS survived long enough to use extended dates.

Sortof. The File system in COS is weird. It do have an sortof OS/8 
compatible file system for the system area, with the different date 
base. But it's not clear if OS/8 would actually be able to read it, as 
the layout of the whole disk is different. COS divide the disk into 
segments, and allocates a bunch of those for the system area, and then 
use the other segments to implement data files.

COS also shares the format of .SV files with OS/8. But I doubt any OS/8 
binary would run under COS. (Well, maybe something that did not use any 
device drivers or USR.)

>> the transfer program
>> available to transfer files to/from OS/8.
> That didn't actually transfer files, which wasn't necessary; IIRC,
> it converted between the COS-310 format for text files (about which
> I know nothing) and the OS/8 format (three 8-bit bytes in two 12-bit words,
> packed with the first two bytes in the low order bits of the words,
> and the third byte split between the four high order bits).

Not entirely. Like I said above, COS has a weird layout of mass storage, 
where you have logical files, which are just numbered. And that is how 
most of the mass storage is used. And those files can also be converted, 
and the transfer program deals with that. In addition, I am not sure 
that OS/8 would be able to figure out any COS disk, since I'm not so 
sure the actual location of the directory files and the data is the same 
between them. So even though the directory format itself is the same, 
that is not necessarily enough to be able to exchange disks.

But yes, in addition, text is also encoded in a different way in COS 
text files.

>> The EDUsystems were in fact having numbers
>> like 10, 20, 25, 30, 40 and 50. No 310 or anything close...
> That's what I remember.  My first PDP-8 was running EDU30 on top of
> OS/8.

Glad we got that sorted. Sorry for the confusion.


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

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