Newsgroups: comp.sys.amiga
Path: utzoo!utgpu!jarvis.csri.toronto.edu!godzilla.eecg!leblanc
From: leblanc@eecg.toronto.edu (Marcel LeBlanc)
Subject: Re: Benchmarks (was: Re: A2620) - really 6502/8085 bashing
Message-ID: <1989Jun19.131400.27557@jarvis.csri.toronto.edu>
Summary: No architecture is perfect
Keywords: 6502, borrow, 8085
Organization: EECG, University of Toronto
References: <17837@louie.udel.EDU> <5017@tekigm2.MEN.TEK.COM>

In article <5017@tekigm2.MEN.TEK.COM> phils@tekigm2.MEN.TEK.COM (Philip E Staub) writes:
>In article <17837@louie.udel.EDU> 451061%UOTTAWA.BITNET@cornellc.cit.cornell.edu (Valentin Pepelea) writes:
>>Excuse me, but you don't know what you're talking about. The 6502 had the most
>>beautiful architecture in its 8-bit era. The way it used its accumulator,
>>indexed registers, and instruction execution was the summum of that bygone era.
>
 ...
>cannot be expanded. Look at the braindamaged definition of the "borrow"
>flag (= not carry) which causes comparison instructions to work backwards from 
>any processor I can name either before or since. How about the scramble for

There's nothing braindamaged about the "borrow", because it's not a borrow,
it's a carry bit!!  If you try to think of it as a flag for borrow, you come
up with the conclusion that it's backwards.  Think of it as a 9th
accumulator bit.  If it's 0 after a subtract, its because a "borrow" occured
from the 9th bit.

	e.g.	1 0000 0001
	     -	  0000 0010
		-----------
		0 1111 1111

> would prevent me from voting for the "golden design" award, but I also seem 
> to remember having problems keeping the pre-indexed and post-indexed registers
> straight. (Let's see here... do you use the x for pre-index or the y?).

There are only two possibilities - it's not that difficult to remember.
Don't tell me that the 8085 didn't also have addressing modes limited to one
register (OK, register pair).  This thinking carried over to the 8086 too.

> Disclaimer: These are, of course, my own personal opinions. You are
> certainly entitled to your own. I admit that my previous programming
> experience (prior to using the 6502) on 8080/8085 and Texas Instruments
> minis biased my opinions. But I just couldn't resist the temptation to

Ditto.  My first programming experiences were in the opposite order: 6502,
8086, 8085, ...  However, my hardware design experience was in the
Intel-first order: 8085, 8088, then 6502, ... (which is consistent with
previous postings on this subject :-) )

Marcel A. LeBlanc	  | University of Toronto -- Toronto, Canada
leblanc@eecg.toronto.edu  | also: LMS Technologies Ltd, Fredericton, NB, Canada
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