"Shoppa, Tim" <tshoppa at wmata.com> wrote:
> "Walter F.J. Mueller" <w.f.j.mueller at gsi.de> wrote:
>>> 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
>>> 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.
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"
Now, compare that to Don Norths picture of the 11/74 front panel:
> 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.
> 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
This is just a short email to let the West Australian members know that
the Artifactory, Perth's very own Hackerspace (in the correct sense of
the word), has started hosting a regular, fortnightly event called
'Classic Computing Appreciation Night'. Several of our current members
have at least a passing interest in collecting, restoring and setting up
classic computers; as this event is being run in conjunction with our
'Circuit Hacking Mondays', there should also be at least one or two
people around to help with the troubleshooting and repair of your
favourite micro- or mini-computer.
The space's electronics facilities include several soldering stations
and CROs, PAL/SECAM/NTSC and analogue RGB monitors, a logic analyser and
an (E)EPROM programmer. Depending on the demand, there may also be a PC
capable of reading from, and writing to, most common 3.5" and 5.25"
floppy disk and tape formats; we also have a fairly respectable
collection of OS installation kits for many DEC, SUN, HP, SGI, IBM
RS/6000, Apple, Commodore and Amiga systems. And for the particularly
adventurous, the space also has a home-designed and built CNC milling
machine and a RepRap 3D printer that could be used to machine or
(literally) print replacement parts and panels.
The space is located in Mount Lawley, and all are welcome. Advice and
ideas are free; workshop use is free for members of the hackerspace, or
$10 waged/$5 unwaged. See
http://wiki.artifactory.org.au/doku.php?id=projects:classiccmp for more
details of the event, and http://hackerspaces.org and
http://en.wikipedia.org/wiki/Hackerspace for information about the
hackerspace movement in general.
Hope to see some of you there,