[Simh] OS development

[Johnny Billquist]

On 2015-06-14 23:30, Rhialto wrote:
> On Sun 14 Jun 2015 at 14:27:12 +0200, Johnny Billquist wrote:
>> Either way, other systems decided to define the two year field as
>> representing 1970 to 2069. Deal with it, or decide to be incompatible.
>
> I noticed that in the RSX version of the On Disk Format, the year is
> represented in what I've known as pig-hexadecimal. That is, the next
> digit after 9 is ':', then ';', '<', etc. Basically, it's simply the
> conversion of the tens of the year number by adding the ASCII value of
> '0', without range check whether it is in the range [0-9].

Right. The ODS-1 date field is unfortunately ugly. Why on earth they 
decided to store it in human readable form is beyond me. But yeah, the 
extension for Y2K was done in the most simple and obvious way... :-)

>>> As for the "New UTC (128 bit) format": that's probably documented
>>> somewhere.  But I haven't found it.  Native VMS times are 64-bits. DTSS
>>> uses an opaque 128-bit structure that may be the basis for this, but a
>>> quick search hasn't turned up a revised DAP spec.  DTSS time includes
>>> precision/accuracy, not just time.
>
> Is that the format as returned by RSX GTIM$, i.e. 8 words which are in
> sequence year since 1900, month, day, hour, minute, second, tick of
> second, ticks per second? If I'm guessing, "New UTC (128 bit) format"
> would be this and be expressed in UTC instead of some unspecified
> timezone.

Nope. The RSX format actually stores 8 16-bit words, which are (in order):
Year, 1900 based.
Month
Date
Hour
Minute
Second
Tick
Ticks/second

It wastes a lot of bits, but it will still last a few ten thousand years...

>> It is more complicated. [...]
>> (Or that is my understanding of the situation anyway.)
>
> That sounds very much like nobody will even have proof they have
> standing to sue anybody...

To be brutally honest, I somehow doubt HP would try to sue somebody in 
the PDP-11 world today, but the question is how much you would like to 
gamble on it.

	Johnny

-- 
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