23 Jun
2004
23 Jun
'04
10:35 a.m.
And presumably stage 3 is to grab a VAX11/7xx
printset,
figure out the microinstruction word, then disassemble the
appropriate bit of the microocde and understand how it works.
If you have access to the appropriate printset, that
might be an option. I don't have it on paper - I know
that some of the 780 stuff is up at bitsavers, but I
don't know whether any of the available prints have
microcode listings.
In all seriousness, you might want to start with
something that is a tad simpler than an 11/780
though!
Actually, I've never done this for VAX microcode,
I did
comment the entire HP98x0 calculator CPU micorocode source,
though (256 locations of 28 bits each).
I went to a DECUS session many moons ago where the
guy was talking about the latest MIPs chips. He
mentioned that while he was at DEC he would while
away the time between whatever bits of stuff he
was actually supposed to be doing, by studying
the VAX-11/780 design. Obviously must have
paid off!
Antonio
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Antonio Carlini arcarlini(a)iee.org