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From: joel@gould9.UUCP (Joel West)
Newsgroups: net.micro.mac
Subject: Re: Apple SCSI HD20 (actually IIgs)
Message-ID: <772@gould9.UUCP>
Date: Sun, 21-Sep-86 19:41:20 EDT
Article-I.D.: gould9.772
Posted: Sun Sep 21 19:41:20 1986
Date-Received: Mon, 22-Sep-86 01:45:27 EDT
References: <491@randvax.UUCP> <154@apple.UUCP> <1791@well.UUCP> <847@Shasta.STANFORD.EDU>
Distribution: net
Organization: Western Software Technology, Vista, CA
Lines: 33
Summary: read the book...

In article <847@Shasta.STANFORD.EDU>, simoni@Shasta.STANFORD.EDU (Richard Simoni) writes:
> Well, there is one point which should be made, although it may or may not
> be relevant to the IIGS vs. 1040ST vs. IBM PC debate.  A general statement
> can be made about computer systems: clock speed <> system performance.
> Why?  Because the number of clock cycles per instruction varies widely
> across processors.  For example (this is off the top of my head and may
> not be exactly right), most 6502 instructions take 2-6 cycles to complete,
> while many Z80 instructions take 15-20 cycles to complete.  Although I'm
> not up on my 16- and 32-bit processors, the point is that comparing clock
> frequencies on machines with different processors is meaningless.

According to the Osborne/McGraw-Hill 65816 book (which I highly recommend
over the Sybek book; there's a 3rd I don't own), 65816/65802 Assembly
Language Programming (Fischer), ... well, I couldn't read the fine
print, so I pulled my Western Digital spec sheet (which has the same
information in larger print).

Addressing mode		"Base no. cycles"
# (immediate)		2	(1 or 2 bytes)
relative		2	-128 to +127 bytes away
direct			3	(add a byte to the direct register
absolute		4	(16 bit within bank specified by bank reg.)

the terminology is identical to the 6502; I'm sorry, but I'm too
lazy to pull out my 68000, 6502, Z-80 and 8086 books to provide
comparisons and figure out what it means.

Hope this sheds some light on the subject.
-- 
	Joel West			     MCI Mail: 282-8879
	Western Software Technology, POB 2733, Vista, CA  92083
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