22 Jun
2010
22 Jun
'10
4:22 p.m.
Don North <ak6dn at mindspring.com> wrote:
Johnny Billquist wrote:
Thanks for sharing that, Don. Now that I see it, I realize that I have
seen it before.
> "Walter F.J. Mueller"
<W.F.J.Mueller at gsi.de> wrote:
>
> >> The reason why I picked a 11/70 and not a J11 as target is because my
> >> goal is a 11/74. I've implemented the IIST already and tested against
> >> the IIST Diagnostic I could find in XXDP (riiab0). A dual core will
> >> fit into a single xc3s1200e of the NEXYS2 board. The work needed is
> >> quite clear and doable (changes on cache, mmu, and cpu core for asrb).
> >> However, I've no plans to implement the CIS, so it will always be a
> >> subset of a 11/74. But for sure fun to do and run.
>
> You do know that the J11 is already designed for mP usage, except that
> DECs testing of that was even more secret than the 11/74?
>
> The 11/74 definitely don't need CIS though. I don't think any
> prototype 11/74 even had it. It was planned for the next generation of
> the machine, that never got built. Anyway, it was to be an option for
> the CPU as far as I know. Just as FPP.
Here's a front panel from a 'real 11/74', the uniprocessor one with
CIS: http://www.ak6dn.com/stuff/1174.jpg 
Note the CIS uADDRS and other CIS status lights
selectable on the rotary
switch on the right.
The marketing dinks appropriated the 11/74 moniker for the wanna-be
11/70mp program because '11/74' sounded better for a 4 way MP system.
Yeah, as usual, name confusion is fun. Interestingly enough, RSX
identifies the 11/70mp as an 11/74.
After the 11/74 CIS COBOL benchmarks came in, the
native PDP-11 CIS
implementation on the 11/74 blew the 11/780 benchmarks away. DEC
marketing did not like this; it made selling business customers the just
released 11/780 more difficult. The decision was made to kill the 11/74
CIS option the day we released it to manufacturing in favor of the new
VAX system.
I wasn't aware that any prototypes ever were produced and came as far as
being functional. I thought it was just paper work that had bee done.
Johnny is right, the 11/74 option was a multiboard set
(just like the
FPP option) that could be plugged into the new 11/74 backplane (which
was an 11/70 backplane with all the CPU and FPP slots pushed down by
four to make room for the CIS option in the first slots).
I wish I had saved more documentation (print sets, microcode listings,
etc) but to my knowledge none of this survives for the 11/74 CIS. Only
my front plex panel which I took as a souvenir.
I was one of the three engineers who wrote the microcode for the CIS
option subsystem (total of 4K words of 96bit wide horizontal microcode).
Nice to hear. Too bad the machine never got to production. It would have
been a nice system...
Johnny
23 Jun
23 Jun
9:12 a.m.
Johnny Billquist [bqt at softjar.se] wrote:
I wasn't aware that any prototypes ever were
produced and
came as far as
being functional. I thought it was just paper work that had bee done.
iirc CASTOR and POLLUX were PDP-11/74s that were actually used by one of
the
DEC PDP-11 software groups for a while. (Or maybe the PDP-11/74 was used
for
a while and then broken up to form CASTOR and POLLUX ... )
Nice to hear. Too bad the machine never got to
production. It
would have
been a nice system...
I've read somewhere that it was full of flat ribbon cables and would
have been a beast to maintain.
Antonio
10:48 a.m.
arcarlini at iee.org wrote:
I've read somewhere that it [PDP-11/74] was full
of flat ribbon cables
and would
have been a beast to maintain.
I've heard that too, but it doesn't make sense. Lots of machines were
full of cables of various sorts, including flat cables, and that didn't
inherently make them especially hard to maintain. It sounds like an
excuse that the marketing department generated, not engineering.
Naturally a four-processor system would be harder to maintain than a
one-processor system. If they didn't make at least some minimal
provisions for serviceability, then it would be more than 4x as hard.
However, with some serviceability provisions, it becomes only slightly
harder. If you read the few docs that exist on the 11/74, the designers
most definitely did include serviceability provisions.
The 11/74 probably would have been *easier* to maintain than the
VAX-11/780 was.
Eric
12:21 p.m.
Eric Smith [eric at brouhaha.com] wrote:
I've heard that too, but it doesn't make
sense.
I read it in an internal DEC NOTES conference but I no longer
have access to any of those. If someone does then at one stage
most of them were indexed by the internal altavista search engine,
so (assuming it is still around) it might be the work of moments
to do a search on "11/74" and find out who made the claim.
Since the machine never shipped, I guess we'll never know how
bad it would have been in the field.
I'd be willing to make room for one despite its clearly poor reputation
:-)
Antonio
5249
days inactive
5250
days old
3 comments
3 participants
participants (3)
-
arcarlini＠iee.org -
bqt＠softjar.se -
eric＠brouhaha.com