[Simh] Simh Digest, Vol 198, Issue 16

[Don North]

On 7/9/2020 6:25 PM, Bob Supnik wrote:
> Yes, the PDP11 Architecture Handbook was a post-facto effort. The J11 was 
> finished; DEC did not intend to do another PDP11 processor. (I wrote a spec 
> for one, primarily as an exercise in trying to do a different microcode 
> structure than the PLA/ROM of the LSI11/F11/J11, but I lost it.) The only 
> formal part of the PDP11 architecture was the Commercial Instruction Set 
> extension, DEC STD 168, which was only implemented by the F11 and the 11/44.

AND the PDP-11/74 CIS option, I might add. Fully implemented, never sold.

It made Cobol run faster on the 11/74 than the 11/780 and marketing didn't like 
that.

So it was shelved after we finished implementing it.

Don North
DEC 1975-1982


>
> Variances in the PDP11 architecture were the driving force behind the 
> precision of the VAX architecture effort; and the problems in how floating 
> point was implemented were the driving force behind Mary Payne's relentless 
> efforts to make VAX floating point "good to the last bit," as she put it.
>
> /Bob
>
> On 7/9/2020 8:55 PM, simh-request at trailing-edge.com wrote:
>> Re: [Simh] pdp11 fails MAINDEC CPU test 14 D0NA
>
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-- 
Don North
AK6DN