Path: utzoo!attcan!uunet!mcvax!enea!tut!pl
From: pl@tut.fi (Pertti Lehtinen)
Newsgroups: comp.sys.amiga.tech
Subject: DBcc Revisited
Message-ID: <4300@korppi.tut.fi>
Date: 20 Jul 88 01:19:55 GMT
Distribution: comp
Organization: Tampere University of Technology, Finland
Lines: 40


	Someone asked about function of MC68000 DBcc instruction.
	I wasn't surprised, because intruction is quite
	hard to understand.

	That came clear to me when I read MC68020 Benchmark
	Report released by Motorola.  There was text about various
	bencmarks and one of them was loop-test, which is in C:

		main()
		{
			long i:

			for(i=0;i<1000000;i++)
				;
		}

	About this benchmark there was text:

	"This benchmark tests both the compiler efficiency and the
	 processor speed. The Alpha Micro MC68020-based machine
	 ( the AM-2075) wiyh the compiler optimizer enabled was
	 able to execute the routine in 0.009 seconds! That is,
	 90,000 microseconds for 1,000,000 iterations, or an
	 effective rate of 11.1 Million iterations/second!
	 The code generated by their compiler was:

		main	move.l	#1000000-1,d0
		loop	DBRA	D0,loop

	"

	So if they don't know how it works,
	how could anyone else?


-- 
pl@tut.fi			! All opinions expressed above
Pertti Lehtinen			! are preliminary and in subject
N 61 26' E 23 50'		! to change without any further notice.