Path: utzoo!attcan!uunet!wuarchive!psuvax1!rutgers!rochester!pt.cs.cmu.edu!dsl.pitt.edu!pitt!willett!ForthNet
From: ForthNet@willett.pgh.pa.us (ForthNet articles from GEnie)
Newsgroups: comp.lang.forth
Subject: Forth Implementation
Message-ID: <1888.UUL1.3#5129@willett.pgh.pa.us>
Date: 21 Oct 90 01:58:41 GMT
Organization: String, Scotch tape, and Paperclips.  (in Pgh, PA)
Lines: 41


 Date: 10-13-90 (16:34)              Number: 4054 (Echo)
   To: ALL                           Refer#: NONE
 From: JONAH THOMAS                    Read: (N/A)
 Subj: 8086 CODE                     Status: PUBLIC MESSAGE

   I've just recently started programming on an 8086 instead of a
 68000, and I wasn't sure how much slower POPs and PUSHs were than
 direct register moves.  So I tested it with the following code in
 Pygmy 1.3.

 ( looking at speed of different assembly commands)
 CODE TEST1   BX AX MOV, AX BX MOV,   NXT, END-CODE
 CODE TEST2   AX POP, AX PUSH, NXT,   END-CODE
 : TESTA -1 FOR TEST1 NEXT ;
 : TESTB -1 FOR TEST2 NEXT ;
 : TESTC 50 FOR TESTA NEXT ;
 : TESTD 50 FOR TESTB NEXT ;
 ( TESTC averaged 20.40 seconds, TESTD averaged 19.34 seconds
    apparently PUSH and POP are faster than register moves on
    this machine.  What a surprise.)

   I figured that since the only difference between them was the two
 assembly instructions, that would be the only thing to make a
 difference in the speed.  But the PUSH and POP combination actually
 came out faster.  This is a memory operation where the other is just
 register to register!  How could it possibly be faster?  Is it 4
 cycles where BX AX MOV, is 5?
   I'm running on an obsolescent 12Mh AT, it's just a standard 80286
 processor.  I don't think it does any fancy cache memory or anything
 like that.
   Can somebody recommend a good book?  I don't remember mysteries
 like this on the 68000, but maybe I've just forgotten....
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