Path: utzoo!yunexus!maccs!cs3b3aj
From: cs3b3aj@maccs.McMaster.CA (Stephen M. Dunn)
Newsgroups: comp.sys.cbm
Subject: Re: what is this chip(65C802)
Summary: 808x may be slow with its memory, but it's better otherwise
Keywords: 6502, 8088, DRAM
Message-ID: <2325@maccs.McMaster.CA>
Date: 3 Apr 89 23:40:02 GMT
Article-I.D.: maccs.2325
References: <16510@cup.portal.com> <7734@killer.Dallas.TX.US> <2310@maccs.McMaster.CA> <89Apr2.223029edt.2745@godzilla.eecg.toronto.edu>
Reply-To: cs3b3aj@maccs.UUCP (Stephen M. Dunn)
Organization: McMaster U., Hamilton, Ont., Can.
Lines: 75

In article <89Apr2.223029edt.2745@godzilla.eecg.toronto.edu> leblanc@eecg.toronto.edu (Marcel LeBlanc) writes:
>>>65c02, etc. take 1 clock cycle. Thus a 8 mhz 6502 would be the
>>>equivalent of a 32mhz 8086-based machine. Considering that 80x6-based
>>The problem with your argument is that you assume that everything on an
>>8086 takes four times as long as on a 6502.  I'd like to see you get a
>>6502 to do a 16-bit signed integer division in under 50 clock cycles
>Since Eric was talking about memory access, there's nothing wrong with his
>argument.  An 8088/86 takes 3 clock cycles per memory access, NO MATTER WHAT
>INSTRUCTION is being executed!  The same is true of the Z80 and 8080.  Eric
>stated 4 clocks/access because these processors need an extra cycle to
>decode the instruction on a fetch.  The 6502 takes only 1 clock/access.
>This is why Dave Haynie was saying that cheap DRAMs wouldn't be enough for
>an 8MHz 6502.  An 8MHz XT on the other hand is much slower, so you can use
>almost any speed DRAM.

   No dispute there ... the point I was trying to make is that we're trying
to compare apples to oranges.  Memory accesses may be (much!) slower on an
8086 or 8088, but beyond that, you can't really compare them to the 65xx
since one is so much older than the other.

>>addressing on a pitiful CPU with two 8-bit index registers.  You're quite
>>right about how dreadfully slow 8086 memory accesses are; however, make
>>sure that you don't get everybody out there in NetLand thinking that they
>>should sell their XT clones and buy a 64.
>Standard clones (today) are faster than the original 4.77MHz that were
>common when the C64 was younger.  When I bought my C128 (ages ago), I
>tried running a simple benchmark on it, then compared with the results on a
>clone that I had borrowed from work.  To make the test "fair", I tested
>floating point addition, since neither machine had floating point hardware.
>I used a simple "FOR" loop in BASIC (you would really have to compare the
>two BASIC interpreters if you wanted to publish 'facts').  As expected, the
>2MHz C128 was 40% FASTER than the 4.77MHz clone.

I don't have a C128 to play around with, but I do have a 64 (with a broken
1541) back home, and I did a C benchmark on it.  The code I used was taken
from BYTE (don't ask me which issue), and it included four tests:  fibonacci,
a floating test, the Savage benchmark, and the standard sieve of Eratosthenes.
On the Fibonacci, the 64 died (not enough stack, so it hung).  On the Sieve,
the 64 had 16.2% of the performance of a real IBM PC.  On the floating
test, it had 64.3% performance, and the Savage said that the 64 had 70.3% of
the performance.  (I suspect, though, that the C compiler on the 64 used the
ROM BASIC floating point routines, which are single-precision, whereas the
PC compiler used the double precision that good C compilers are supposed to
use.

Now, of course I realize that this is a comparison of the two compilers as
well as the hardware, but it shows just how much slower the 64 is.  One
neat thing, though, which shows that the 8086 family has some inefficiencies,
is that when you adjust the figures to take into account the difference in
clock speeds, the 64 had 75.6% of the performance of an XT (based on the
sieve).

Anyway, I'm going to stick with my AT clone.  The 64 was nice while its
disk drive lasted, but it just can't hope to compare with machines using
much more recent technology.

Besides, there's such a great variety of software for the PC family, and
I'm just continuing on here because our news posting program requires me
to half more than half new text.

f
i
l
l
e
r

That should about do it.

Regards,
-- 
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! Stephen M. Dunn, cs3b3aj@maccs.McMaster.CA ! DISCLAIMER:           !
! I always wanted to be a lumberjack! - M.P. ! I'm only an undergrad !
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