Microcode Assist for VSAPL 
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 Microcode Assist for VSAPL


 The System 370/145 had a microcode assist for VSAPL; this was said to be the
reason that VSAPL bytes were stored wrong way 'round (flipped wrt XM6 APL).
Interestingly, Roger Moore once looked into the microcode assist (you used to
get the listing in a box when you bought the CPU - I still have one :-). He
claimed that the step, apparantly intended to make things like scans on boolean
data go faster, actually slowed them down.

 Jim Ryan's candidate, the BSP, and the microcode assist, can be plausibly
described as 'APL machines'. After all, the 370/145, for example, only
executed System 370 instructions in emulated mode (they were basically all
microcoded), so the APL assist brought at least some of APL onto the same level
as a 370 assembler program. Most of the burroughs machines were very heavily
microcoded as well (in at least the case of the B1700, the microcode was
part of a running program's context, and more than one set could be active at
once during normal machine operation).

.../Leigh

--------------------------------------------------------
  So if I waste words now, in truth
    You must not blame love.    His early rage
  Had force to make me rhyme in youth,
    And makes me talk too much in age.
                 ... The Miller's daughter,  Alfred Lord Tennyson
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Mon, 21 Dec 1998 03:00:00 GMT  
 
 [ 1 post ] 

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