Self modifying code, lambda calculus - Re: ENIAC programming

Jon Elson elson at
Fri Sep 18 11:21:13 CDT 2015

On 09/18/2015 08:45 AM, tony duell wrote:
>>> As far as I know, the VAX11/730 (There is one next to me waiting for me to have time
>>> to restore it) has the microcode entirely in RAM. Classic PERQs (3 in the next room) have
>> The PDP-11 console loads the microcode from disk then mostly just sits there
>> looking pretty whilst the VAX runs.
> The 11/780 has a PDP11 to load the microcode (I think) but the 11/730 makes do with an
> 8085. After booting I think that handles the console port still.
> -tony
780's had a board of fixed microcode, and then a WCS board 
was added in later revisions (and all machines in the field 
had to be upgraded) to add some additional code to handle 
added instructions used by the OS (at least for VMS, don't 
know if BSD used it).  The WCS microcode was in a file on 
the LSI-11's floppy, and it was called in at a certain point 
of the VMS boot sequence.  That caused a line to print 
during the boot.  The typical dot matrix printer console on 
the 780 was also connected to/through the LSI-11.


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