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'Wanted: Microchip's "The truth about AVR"'
2000\03\26@233240 by Jim Robertson

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Hi Piclisters.

On Eric Smith's PIC page there is a dead link to a file on the
microchip web site called "The truth about AVR"

Does anyone have an actual copy of the "The truth about AVR" as
I would like to read what microchip had to say.

Thanks for any help.
Regards,

Jim Robertson
NEWFOUND ELECTRONICS
________________________________________
Email: spam_OUTnewfoundTakeThisOuTspampipeline.com.au
http://www.new-elect.com
MPLAB compatible PIC programmers.
________________________________________


'Wanted: Microchip's "The truth about AVR"'
2000\04\07@021214 by Andrew Sempere
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I wondered if you found a copy of this... I'd like to read it too.

Jim Robertson wrote:
>
> Hi Piclisters.
>
> On Eric Smith's PIC page there is a dead link to a file on the
> microchip web site called "The truth about AVR"
>
> Does anyone have an actual copy of the "The truth about AVR" as
> I would like to read what microchip had to say.
>
> Thanks for any help.
> Regards,
>
> Jim Robertson
> NEWFOUND ELECTRONICS
> ________________________________________
> Email: .....newfoundKILLspamspam@spam@pipeline.com.au
> http://www.new-elect.com
> MPLAB compatible PIC programmers.
> ________________________________________

2000\04\07@023920 by William Chops Westfield

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   > Does anyone have an actual copy of the "The truth about AVR" as
   > I would like to read what microchip had to say.

It wasn't worth reading.
It's to microchip's credit that they got rid of it.

The best point made against the AVR, IIRC, was that Atmel measured
program memory in bytes (with two bytes per instruction), and microchip
measaured program memory in words (of assorted odd widths.)  So a 1K
atmel avr holds as many instructions as a 512word PIC.  (these days it's
also cheaper than a 512 word PIC...)

BillW

2000\04\07@033501 by steve

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> I wondered if you found a copy of this... I'd like to read it too.

It's on the July 99 CDROM if you have one of those kicking around.
\Download\Lit\Truth\Truth.pdf.

It's a 160k pdf (18 pages). If someone wants to put it on a site I'll
email them a copy.

Steve.


======================================================
Steve Baldwin                Electronic Product Design
TLA Microsystems Ltd         Microcontroller Specialists
PO Box 15-680, New Lynn      http://www.tla.co.nz
Auckland, New Zealand        ph  +64 9 820-2221
email: stevebspamKILLspamtla.co.nz      fax +64 9 820-1929
======================================================

2000\04\08@015736 by David E Arnold

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hi BillW,

I'm sorry, I didn't quite get what you said, could you repeat?
Are you saying that the Microchip showed that the AVR doesn't
store data and code as well as a PIC? How serious is this problem,
I was considering using an AVR or a PIC for my next
project.

-Dave





William Chops Westfield <.....billwKILLspamspam.....CISCO.COM> on 04/06/2000 11:38:38 PM

Please respond to pic microcontroller discussion list <EraseMEPICLISTspam_OUTspamTakeThisOuTMITVMA.MIT.EDU>

To:   PICLISTspamspam_OUTMITVMA.MIT.EDU
cc:    (bcc: David E Arnold/SYBASE)
Subject:  Re: Wanted: Microchip's "The truth about AVR"




   > Does anyone have an actual copy of the "The truth about AVR" as
   > I would like to read what microchip had to say.

It wasn't worth reading.
It's to microchip's credit that they got rid of it.

The best point made against the AVR, IIRC, was that Atmel measured
program memory in bytes (with two bytes per instruction), and microchip
measaured program memory in words (of assorted odd widths.)  So a 1K
atmel avr holds as many instructions as a 512word PIC.  (these days it's
also cheaper than a 512 word PIC...)

BillW

2000\04\08@021040 by David VanHorn

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>I'm sorry, I didn't quite get what you said, could you repeat?
>Are you saying that the Microchip showed that the AVR doesn't
>store data and code as well as a PIC? How serious is this problem,
>I was considering using an AVR or a PIC for my next
>project.

Not at all.
It's one word per instruction.
They call out the rom size in bytes.
8kbyte rom, 4kwords.
In other machines, the equivalent instr might be 2 or 3 bytes long.
uChip has some 12 bit word machines, they call 4kwords 4k

Atmel shouldn't have done it, uChip was making a mountain out of a molehill
with it.
FWIW: I've only ever used 3/4 of an avr at max.

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2000\04\09@102957 by Marc

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> The best point made against the AVR, IIRC, was that Atmel measured
> program memory in bytes (with two bytes per instruction), and microchip
> measaured program memory in words (of assorted odd widths.)  So a 1K
> atmel avr holds as many instructions as a 512word PIC.  (these days it's
> also cheaper than a 512 word PIC...)

I think specifying the AVRs in kbytes instead of kwords is reasonable
(despite the stupid mixture of words/bytes in their assembler).  All
AVRs except for the S1200 can read-access their code memory.  You
can store data (for example text or tables) in the code space and
read them at byte granularity.

The PICs don't let you do that (at least those a few years ago).  On
a PIC you always use a word for an item to store.  Be it a byte, or
an instruction.

A 512kword PIC lets you store at maximum 512 bytes of graphics data
for example, or 512-x bytes plus x instructions of output code.

A 1024kbyte AVR (except for the S1200) lets you store 1024 bytes
of graphics data, or 1024-(2*x) bytes plus x instructions of
code.


It doesn't make much of a difference in very tiny projects that don't
have lots of data anyway.  But it is really essential in large
projects with tens of kilobytes of data.  One of my projects has
40kb of data at the moment and 50kb of code.  If that data would
occupy 1 word per byte I would have run out of code flash already
(128kb available).



Keep in mind that the AVR architecture is not only a tiny 8bit
controller without busses, but an open 8bit core processor. I have
already seen AVRs execute code from pseudo-van-neumann off-chip
memories (something that no Atmel _standard_ AVR parts do to date).

The architecture is a CPU as well, not just an MCU.

Have you ever seen a Pentium specify its address space in
instructions instead of bytes?  Bought a new 16M-Instructions SIMM
stick for your PC?

Specifying kwords makes sense for PICs because you can't use
its memory in any smaller granularity.



(don't perceive this as an attack against PICs. I'm just neutrally
explaining why I think kbytes is appropriate for AVR and not
a marketing trick, and why kwords are more convenient for PICs).

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