From: Steven Malikoff
I was lucky to find an original 11/05 print set dated
1973. For what
it's worth, the microcode listing in my doc is Revision B
Do note that a lot of the PROMs on those boards aren't actually 'microcode',
and aren't covered in that listing. For instance, on the M7261 (control)
board, there are 7 which aren't 'microcode' (list drawn from the 11/05
article on the Computer History wiki):
A01A2 = E12 = Bus Request -> Grant processing
A02A2 = E30 = Internal address decode (first stage)
A07A1 = E68 = Internal address decode (second stage)
A09A1 = E69 = Internal address decode (second stage)
A09A2 = E101 = Branch utest service
A13A1 = E90 = Internal interrupt acknowledge
A14A1* = E100 = Console switch control
and 10 which are:
A04A2 = E92 = Next instruction (high bits)
A05A2 = E93 = Processor Status Word control
A07A2* = E95 = Bus control
A10A2 = E103 = Next instruction (low bits)
A11A2 = E104 = ALU operation select
A12A2 = E105 = Branch utest
A13A2 = E106 = Multiplexor control
A14A2 = E107 = Bus control
A15A2 = E94 = ALU control
A16A2 = E96 = Miscellaneous
And I haven't included the 11 PROM chips on the M7260 (Data paths) board,
none of which are 'microcode'. So those 'microcode' listings only cover
about
1/3 of the PROM chips in the CPU; so one can't use just the microcode
revision level to tell you what's what.
E.g there are two chips different between the C and E etch levels of the
M7261: A07A2 and A14A1 (marked with a '*' above); one is 'microcode', one
isn't.
BTW, when you say that the microcode listings in your 1973 print set are
"Revision B", are you referring to the "Microprogram Flow",
"Microprogram
Symbolic Listing", or "Microprogram Binary Listing", because they can be
at
different revision levels (given in the box in the extreme lower right
corner)?
E.g. the ones in the KD11-B prints in the GT40 print set (dated February
1973) are 'B', 'C' and 'C', respectively; the hard-copy set I have
(not dated
explicitly, but apparently mid-1972, given the modification date on the
'Index' sheet) has 'B', 'B' and 'B'.
it is *exactly* the same printout as in the the
Bitsavers doc Revision
C
You mean the July 1976 set, the ones with microcode revision levels (as
above) of 'C', 'E', and 'E', right?
That is M7261 etch revision 'F', which uses quite a few different PROM chips
from the earlier ones, so I'd be fairly surprised
if the microcode was
actually identical. I think you'd have to look at every bit
to be sure; the
data on which chips changed, here:
http://gunkies.org/wiki/PDP-11/05#Control_PROMs
would allow anyone who wanted to actually do that to focus in on specific
columns of the microprogram to look for differences.
(In fact, the 'F' etch rev has one less PROM chip than the 'E' etch rev,
but
I suspect - i.e. I haven't checked the exact function of each chip on those
etch levels - that it's not a micro-program chip, though: there's one less
32x8 PROM chip, and those are generally used for control functions, the
microprogram chips are all 256x4.)
Noel