Help: PDP-11 instruction classification
Steven M. Schultz
sms at moe.2bsd.com
Wed May 10 13:32:53 AEST 2000
Hi -
> From: lars brinkhoff <lars at nocrew.org>
> Does this mean that an unexpanded 11/40 has no EIS instructions,
Quite correct.
> but with the EIS option, it has more instructions than an 11/45?
Adding the EIS brings an 11/40 to the same level as an 11/45 without
floating point.
> GCC seems to think that all PDP-11 models has ASH, but this seems
> wrong. It's only in EIS, right?
Yes - that's part of the EIS. Standard on the 11/45, 11/70 (and the
later KDJ-11 systems such as the 11/53, 73, 83,etc)
> CIS: commercial instruction set (opcodes 0x7d00..0x7eff).
Not a popular option at all. At the time DEC was trying to make the
11 more of a COBOL machine but the CIS option was too little, too late
and expensive (plus it wouldn't fit as I recall on a 11/70 - just the
11/44 and newer).
...
> MODF, ADDF, SUBF, and DIVF (opcodes 0xf000..0xffff).
>
> Would this be correct?
Looks right to me.
> FIS and CIS isn't imlemented in Supnik's simulator, and I haven't
> found any documentation. Does anyone know more about those? Why
> is there both an FADD and an ADDF instruction?
Two different machines. The FADD was part of the FIS option for the
11/40 only (I don't recall ever hearing of someone adding the FIS
to a 11/45 or 70). The 11/45, 70 and later all had the FPU
as an option or standard (the KDJ-11{A,B} had the instructions standard
but you could buy (~$600 at the time) an accelerator chip to speed
them up). I don't think there were any models after the 11/70
that used the FIS.
There was also the CSM (Call Supervisor Mode) instruction which was
on the 11/44 only (or did it make it into the later KDJ-11 line as
well - I forget).
Steven Schultz
sms at moe.2bsd.com
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