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An early Lisp Machine?

April 26, 2017early LISP Machine

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An early Lisp Machine?

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——————————– Of cours= e, we all know how CAR/CDR came from the address and decrement part of 704/7090 instructions. But tag bits where also prese= nt. The 36-bit words could be considered as: +-+-+-+-+= -+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ |opcod|= decrement ( 15-bit) &n= bsp;| tags| address ( 15-bit) &nbs= p; | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+= -+ |s 1 2|3 4 5 6 7 8 9 0 1 2 3 4 5 6 7|8 9 0|1 2 3 4 5 6 7 8 9 0 1 2 3 = 4 5| |0 0 0|0 0 0 0 0 0 0 1 1 1 1 1 1 1 1|1 1 2|2 2 2 2 2 2 2 2 2 3 3 3 = 3 3 3| | | &n= bsp; &nbsp= ; | = | &= nbsp; &nbs= p; | There are instructions to get or set each of = the fields: the operation code, the decrement, the tags and the address.= STO CLA store and load a full word (CONS) in the 36-bit = accumulator AC. STP store the prefix (ie. operation = code, ie. “tags for CDR”). STD &n= bsp;store the decrement. STT store th= e tags (“tags for the CAR”). STA = store the address.