30 Jun
2010
30 Jun
'10
8:27 a.m.
"Shoppa, Tim" <tshoppa at wmata.com> wrote:
"Walter F.J. Mueller" <w.f.j.mueller at
gsi.de> wrote:
Yes, I know.
I'll reply to this one last time, and then I'll give up.
Don North reported that he had been a part of the team that had written
the CIS microcode for the 11/74 CPU.
I commented that I thought the 11/74 CPU had only been a paper product.
Don North also pointed out that marketing "stole" the 11/74 moniker for
the 11/70mP system.
Now, throughout this discussion, we need some way of separating what we
are talking about. DEC internal project papers seems like a good start.
There we have the 11/70mP, which is a modified 11/70 with just the
addition of the ASRB cache bypass and memory interlock, as well as the
cache bypass bit in the PDR, and a cache bypass bit and flush control in
the cache control CSR.
The 11/74 is a total redesign of the 11/70 CPU, with the same
modifications as the 11/70mP, but also the addition of the CIS, removal
of one Massbus, and redesign of a whole bunch of CPU boards, including
removing one clock signal not used, and the addition of new clock
signals and control signals required by the CIS.
I'm only talking CPUs here, not systems.
Another way to name them would perhaps be:
KB11-B - Old 11/70 CPU with synch FPP.
KB11-C - New 11/70 CPU with asynch FPP.
KB11-CM - MP modified KB11-C
KB11-E(?) - The new 11/74 CPU with asynch FPP and CIS.
I seem to remember reading somewhere that the 11/74 CPU were to be
called KB11-E, but I also have this nagging feeling that KB11-E might
have been the 11/44, or possibly the 11/60.
Now, as I myself pointed out, RSX regards the 11/70mP as an 11/74, and
that is also what the CPU identification code in RSX calls it.
But if we call this an 11/74, what shall we call the 11/70 with CIS?
So, for the purpose of this thread, I decided to go with Don Norths
naming, and call the 11/70 modified for multiprocessor operations the
11/70mP. If you look at the picture on your site, Tim, you'll also
notice that the text on the front panel actually says something like
"PDP-11/74 MP". (Not sure about the /74, but you definitely see the
"MP"
part. (http://www.trailing-edge.com/~shoppa/1174Xopen.jpg)
Now, compare that to Don Norths picture of the 11/74 front panel:
http://www.ak6dn.com/stuff/1174.jpg.
> 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.
>
> The 11/74 wasn't marketed, as pointed out in this thread, but a
> few systems were build by DEC. A picture of such 11/74 system
> was made available by Tim Shoppa, see
>
> http://www.trailing-edge.com/~shoppa/1174Xopen.jpg
>
> You'll nicely see the four CPUs.
Yes, I know of these systems. However, that is
not an 11/74 on that
picture, but an 11/70mP. There is a difference...
As pointed out, the 11/70mP was marketed as an 11/74, but it's a
different CPU.
The easiest way to see that this is a picture of
an 11/70mP is by
looking at the lower rotary switch, which only have four positions, and
not eight (which the 11/74 have). So no CIS on this machine.
The only 11/74 picture I've seen so far is
the silk screen panel picture
posted a few days ago. Unfortunately I've already forgotten the name
(I'm lousy with names, sorry) of the person who posted it, and who also
worked on the 11/74 CIS microcode.
The machine on that picture is probably CASTOR::
by the way.
The people who work with/maintain CASTOR:: call it a 11/74, FWIW. 
They never used the term "11/70mP" in front
of me for sure. I would occasionally elicit comments about multiprocessing on 73's or
93's but it always came back to "our 11/74 does it THIS WAY" because that
was the working example.
I'm not disagreeing with you, Tim. I'm just trying to point out that we
have two different CPUs here, one of which I thought was never made, but
Don actually claims that it did exist, even if just as one prototype.
The system was called an 11/74 everywhere, but for the purpose of this
discussion, we need to make a distinction between the CPUs.
I'm not saying that "11/70mP" is wrong,
indeed it's used in some of the drawings and memos to describe what was commonly
called the 11/74.
Yes.
CIS was real important to some DECcies circa late
70's for some Cobol requirement but coming from the real-time side none of us ever
cared. We'd just run across machines that had this unneeded option.
Indeed. And the 11/70 don't have it, nor does the 11/74 systems that
ever were used.
CASTOR:: was 4 CPUs, by the way, while PHEANX:: was only 2, if I
remember right.
Johnny