Path: utzoo!utgpu!water!watmath!clyde!rutgers!cmcl2!nrl-cmf!ames!sdcsvax!nosc!marlin!aburto
From: aburto@marlin.NOSC.MIL (Alfred A. Aburto)
Newsgroups: comp.sys.amiga
Subject: Re: Still More 68020 Questions
Message-ID: <1024@marlin.NOSC.MIL>
Date: 26 Jan 88 23:42:25 GMT
References: <9750@ccicpg.UUCP> <3204@cbmvax.UUCP>
Reply-To: aburto@marlin.nosc.mil.UUCP (Alfred A. Aburto)
Organization: Naval Ocean Systems Center, San Diego
Lines: 58

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These are the Dhrystone V1.1 results with the Turbo-Amiga (68020) with
Cache ON and OFF, and with 16-bit and 32-bit memory.  50,000 iterations
were conducted with the 'register' option selected using Manx Aztec C
V3.4B.

System        CPU  Memory  Clock  Cache   Time    Dhrys/sec  Gain Over
		   (bits)  (MHz)          (sec)              Amiga 1000

Turbo-Amiga  68020   32    14.32   ON     16.48     3034        2.79
Turbo-Amiga  68020   32    14.32   OFF    18.20     2747        2.53
Turbo-Amiga  68020   16     7.16   ON     42.72     1170        1.08
Amiga 1000   68000   16     7.16   ---    46.00     1087        ----
Turbo-Amiga  68020   16     7.16   OFF    53.76      930        0.86
 
The Turbo-Amiga with 16-bit memory, 68020, and Cache OFF is a highly
degraded mode of operation.  With the Cache ON some minor to moderate
performance improvements with 16-bit memory can be achieved.

Of course different test programs and different compilers will yield
different results.  For example, with a program (FLOPS) which estimates
the average time to do double precision adds,subs,muls, and divides with
an output in thousands of floating-point operations per second (KFLOPS) 
we get (with software floating-point):

                                   ------- 68020 Cache ON --------
System       Language               CPU    Memory   Clock   KFLOPS  Gain Over
		       		           (Bits)   (MHz)           Amiga 1000
Turbo-Amiga  Lattice C V4.0        68020     32     14.32    15.3   2.94
Turbo-Amiga  Lattice C V4.0        68020     16      7.16     5.7   1.10
Amiga 1000   Lattice C V4.0        68000     16      7.16     5.2   ----

Turbo-Amiga  Absoft F77 V2.2C      68020     32     14.32    12.7   3.97
Turbo-Amiga  Absoft F77 V2.2C      68020     16      7.16     6.2   1.94
Amiga 1000   Absoft F77 V2.2C      68000     16      7.16     3.2   ----

Turbo-Amiga  Aztec C V3.4B(mx.lib) 68020     32     14.32     8.7   3.78
Turbo-Amiga  Aztec C V3.4B(mx.lib) 68020     16      7.16     4.4   1.91
Amiga 1000   Aztec C V3.4B(mx.lib) 68000     16      7.16     2.3   ----

Turbo-Amiga  Lattice C V3.03       68020     32     14.32     4.7   4.27
Turbo-Amiga  Lattice C V3.03       68020     16      7.16     2.5   2.27
Amiga 1000   Lattice C V3.03       68000     16      7.16     1.1   ----

The 68020 with 16-bit memory (Cache ON) does provide performance        
improvements over the 68000, but the amount of improvement is program
and compiler dependent.  In some cases only a slight improvement (8% with
the Dhrystone) but in others maybe a factor 2 improvement (Absoft F77 above).
To get the most out of the 68020 we need to utilize 32-bit memory at higher
clock speeds as much as is possible in our programs --- then improvements
of nearly a factor of 3 over the 68000 should be fairly consistent it 
appears.

Al Aburto

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