[Simh] pdp7/decsys bug?

[Davis Johnson]

Robert Armstrong wrote:

>>On the other hand, TSS/8 seems to be calling unimplemented 
>>instructions all the time. It stopped almost as soon as I ran
>>it with the above instruction. 
>>    
>>
>
>  TSS/8 uses unimplemented IOTs (i.e. 06xxx opcodes) as monitor calls.  With
>the PDP-8 User Mode flag set, _all_ IOTs trap to the OS whether the hardware
>actually implements them or not, and the TSS/8 designers simply picked some
>unimplemented IOTs as the official way to call monitor functions.  Is that
>what you're seeing??
>
>Bob Armstrong
>
>_
>
Didn't TOPS 10 do somthing similar? I remember from long time ago when I 
was doing MACRO-10 that system calls were UUO (Unimplemented User 
Opcode) instructions.
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