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From: sdh@thumper.UUCP
Newsgroups: comp.sys.apple
Subject: The speed of the 6502
Message-ID: <414@thumper.UUCP>
Date: Tue, 24-Feb-87 11:34:02 EST
Article-I.D.: thumper.414
Posted: Tue Feb 24 11:34:02 1987
Date-Received: Fri, 27-Feb-87 00:19:59 EST
Lines: 16


The 6502 runs at 1.02 Mhz.  I do not know how much of this time goes directly
to instructions.

One of the reasons that the Apple could go faster than the 4Mhz TRS-80 is that
the TRS-80 was Z-80 based, and the z-80 instructions take quite a good number
of cycles to execute (roughly 4 times as many as a 6502).

For example and indexed load in for the 6502 takes 3 or 4 cycles (depending
on certain specific conditions).  While I do not know the specifics ofr the Z-80,
it will far more cycles than 3 or 4.  When you think about it, 3 or 4 is
pretty darn efficient.  I think cycles are determined by the number of microcode
steps required to do an instruction.

Retief of the CDT
bellcore!sdh