>V5.05 of RT-11 which was released in October 1989. As for the
>real advantage of the PDP-11/93, with all 4 MBytes of memory
>on board and 8 serial ports, it effectively replaced 4 quad slots
>with just ONE quad slot.
And, with the memory on-board, it is almost (though not quite) like
having all of main memory cached, since it probably doesn't require
the same bus accessing/sequencing as other memory.
>What Megan Gentry has stated is correct, although I note that the letter
>"A" is present when the dual M8192-A boards are used. Also, I am not
You're right... I just checked the source for RESORC and found it...
>(b) The different rev levels for the J11 CPU chip were
>needed due to reasons which only DEC might wish to
>reveal, but some reliable stories are spoken of a bug
>with the floating point instructions using early rev levels
>with the KDJ11-BF and the 18 MHz clock speed.
>In addition, since the PDP-11/93 CPU boards were
>run at 20 MHz, these PDP-11/93 boards probably
>required a specific rev level as well?
In fact, I have taken a KDJ11-B board with an 18Mhz clock,
removed the clock chip and replaced it with a 20Mhz clock
and the system ran solidly (I still have it). It also
correctly identifies, in the boot rom, that the machine has
a 20Mhz clock...
>(c) I have also heard rumours that DEC (or a contract
>company) developed a much faster CPU, but it was never
>brought to market - possibly due to perceived competition
>against the MicroVAX II systems. A company by the name
>of Harris was mentioned in the mid 1980s.
There were rumors of the 11/74 being killed because it
was faster than the soon to be released 11/780... but
again, that was rumors, I certainly was not privvy to
the performance numbers...
>Can Megan Gentry provide any information about a floating
>point bug for the KDJ11-BF? Also any information about
>the different rev levels of the J11 CPU chip? Or does anyone
>else know of the reasons for the different rev levels of the
>J11 chip, let alone what specific changes were made?
I don't have specific information about an FP bug... I remember
that some boards couldn't have the FPA installed due to some
bug but don't have the specifics.
>With reference to your luck about putting the parts
>of a PDP-11/84 together with the correct memory,
>perhaps you had some help or maybe the memory
>was already inside the backplane. After all, it could
>not have been used anywhere else, so it might well
>have been just left in the backplane and been there
>when you "grabbed parts".
Nope, I would have been the one who did it, alone, since
I was the recognized scrounge for the group... I was always
checking the halls in the mill for parts discarded from
other groups...
>Also, can you provide any insight as to why DEC
>stopped development on PDP-11 CPUs when
>other companies provided faster CPU chips much
>later than when DEC stopped?
I don't have any hard info on that... the powers-that-be probably
decided that strategically they wanted VAX...
Heck, at least 2, and maybe three managers of the RT-11 group seemed
tasked with the responsibility to bring RT development to a close (as
early as 1984 or so) and we lasted until 1992. (At the end, we were
doing work on both the tail end of RT-11 V5.6 and ramping up on
working on Ultrix 4.2)
Megan Gentry
Former RT-11 Developer
+--------------------------------+-------------------------------------+
| Megan Gentry, EMT/B, PP-ASEL | email: mbg at world.std.com |
| Member of Technical Staff | megan at savaje.com |
| SavaJe Technologies, Inc. | (s/ at /_at_/) |
| 100 Apollo Drive | URL:
http://world.std.com/~mbg/ |
| Chelmsford, MA 01824 | "pdp-11 programmer - some assembler |
| (978) 256 6521 (DEC '77-'98) | required." - mbg KB1FCA |
+--------------------------------+-------------------------------------+
Received on Sun Dec 14 2003 - 13:01:16 GMT