This Sentence is False (DEC-20)

[Dave Brower]

> On a Dec-20, you have a huge number of strange instructions, including :
...
> skipn : skip never
> jumpn : jump never

I always assumed these instructions 'existed' out of dedication to
orthogonality in the instruction set.  The DEC 10/20 seemed to have
about a bizzilion instructions that boiled down to NOP.  The advantage
was that it was easy to learn the mnemonics, since they were all
constructed in a regular fashion.  It was also very easy to create and
examine object code:  all the instructions are the same size, and the
scheme for modifying operand types is also very regular.  Stanford had
an ungodly quick one-pass assembler called FAIL that worked because it
always knew how big an instruction was (one 36 bit word), and because it
had the linker try to resolve all of the forward references.
-- 
{amdahl|dual|sun|zehntel}\		|"If his brains ran down, how could
{ucbvax|decvax}!mtxinu---->!rtech!daveb |he talk?"
ihnp4!{phoenix|amdahl}___/		|"Happens to people all the time...."