Help: PDP-11 instruction classification
Johnny Billquist
bqt at Update.UU.SE
Wed May 10 17:11:24 AEST 2000
On Tue, 9 May 2000, Steven M. Schultz wrote:
Hi, all.
> > From: lars brinkhoff <lars at nocrew.org>
...
> > 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).
Actually, not even those. It's the 11/44 and the KDF-11 based systems
only, which means 11/23 and 11/24.
...
> > 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.
FIS is only for 11/35, 11/40 and the LSI-11. And it's a real brain-damaged
thing too. Lucky us FPU came along.
> 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).
Yes, CSM is in the J-11. There is also TSTSET in J11, but I wonder if
anyone uses it.
Speaking of CSM, by the way. Slighty off-topic perhaps, but in
RSX-11M-PLUS they used to have a rather complex way of getting to
supervisor mode in user programs, since the 11/70 didn't have CSM. Then
came the J-11, and DEC changed things around on systems having CSM to use
this instruction instead. It turned out that this improved code quite a
lot, so they implemented the CSM instruction by emulation on the 11/70 as
well.
Johnny
Johnny Billquist || "I'm on a bus
|| on a psychedelic trip
email: bqt at update.uu.se || Reading murder books
pdp is alive! || tryin' to stay hip" - B. Idol
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