Question regarding PIC 18 series performance verses MSP430F149

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Question regarding PIC 18 series performance verses MSP430F149:

Currently I'm using a TI MSP430F149 running at 12Mhz (overclocked) in
a prototype.  For various reasons I'm considering using a PIC 18Fxxx,
but want to know before I bother porting the code/building hardware if
the PIC running at a 10MHz instruction clock will give me similar
performance to the MSP430 at 12Mhz.  Here are some details of my
application.

- Application mixed C and assembly source

- 2 A/D channels sample rate 25kHz

- only other I/O is a single output pin

- Software algorithm contains a Least Squares Fit on 8 A/D samples
(several 8x8 multiplies)

- Otherwise the software involves mainly counting samples and stepping
through simple state machines based on the data

-MSP430 at 12Mhz takes 38uSec to process both data channels  between
40uSec samples

The PIC A/D seems more than adequate and the 18 series part have the
hardware multiplier that I need.  My uncertainty is that although the
PIC has the Harvard Architecture and other features that allow all
instructions to be single cycle is it really more speed efficient than
a part like the MSP430 which has single cycle register to register
instructions, but variable clocks per instruction on RAM and
peripheral accesses depend on addressing mode etc.

My question has more to do with PIC performance in general rather than
a specific device comparison.

Re: Question regarding PIC 18 series performance verses MSP430F149
On 17 Dec 2003 07:33:08 -0800, the renowned snipped-for-privacy@hotmail.com

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You do know the PIC has an effite 8 x 8 hardware multiplier compared
to the manly 16 x 16 multipler on (many of) the MSP430s? If that's all
you need, fine.

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I have not compared the two in an organized way, but I suspect a 40MHz
18Fxxx PIC will run maybe 1/3 slower than a 12MHz MSP430, depending on
the exact instructions. Much slower than that if you're doing 16 bit
or better math. On some floating point comparisons I made, the MSP430
was much faster even at a kosher 8MHz (supposedly 25MHz is coming
RSN).

But, for your particular application, you've only got to write a few
hundred instructions and simulate to find out.. suggest you do that.
 

Best regards,
Spehro Pefhany
--
"it's the network..."                          "The Journey is the reward"
snipped-for-privacy@interlog.com             Info for manufacturers: http://www.trexon.com
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Re: Question regarding PIC 18 series performance verses MSP430F149
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I'd certainly say this is ballpark right, possibly even over-estimating
the PIC18's horsepower - I think it would be slightly than your guess.
I'd estimate that a 40 MHz PIC would be something like 58% of the
processing power of a 12MHz MSP430.

(My rough calculation starts from the assumption that a 48/12MHz PIC18
running capable of running everything single-cycle, if such a device
existed, would be "roughly equivalent" to a 12 MHz MSP430; so scale by
a factor of 5/6 for clock speeds, and then scale by a factor of about
0.7 for the two-cycle instructions on the PIC which seem to reduce a
10MHz device to about 7 MIPS - we've measured this on a few mixes!)

pete
--
snipped-for-privacy@fenelon.com "There's no room for enigmas in built-up areas."

Re: Question regarding PIC 18 series performance verses MSP430F149
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Many instructions on the PIC18 are not single-cycle. We found that a
40MHz PIC18 (i.e. 10MHz instruction cycle) typically operated at about
7 MIPS (PIC18 MIPS, so about the same as most 8/16-bit baby micros)
over typical mixes of compiler-generated code.

pete
--
snipped-for-privacy@fenelon.com "There's no room for enigmas in built-up areas."

Re: Question regarding PIC 18 series performance verses MSP430F149
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I've used both and they're both nicely fast. But the F149 is faster
because it's really a 16 bit processor, while the PIC18 is really an 8
bit processor. Obviously this affects arithmetic, but also "normal" code
such as pointer work. And of course the F149 has a more -uh- conducive
memory model. Take a look at the instruction sets.

--
Mike Page BEng(Hons) MIEE           www.eclectic-web.co.uk


Re: Question regarding PIC 18 series performance verses MSP430F149
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It's also worth pointing out that code quality on PIC18 compilers varies
very widely. Microchip's own compiler started off appalling and has
improved a bit. IAR's compiler started off appalling and has become
fairly tolerable. ;P

Don't expect to be able to port code that expects a single unified
memory space to the PIC easily though (e.g. code that jumps along pointer
chains through ROM and RAM). IAR offer a generic tagged pointer type that
can address both code and data space (and a Godsend it is sometimes)
but using it is expensive. You quite simply can't do that with the
Microchip compiler.

pete
--
snipped-for-privacy@fenelon.com "There's no room for enigmas in built-up areas."

Re: Question regarding PIC 18 series performance verses MSP430F149
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Since it is very unwise to overclock a CPU in anything intended to
become a product, perhaps a 16MHz mega-AVR might be worth considering in
addition to the PIC.  Besides the faster clock than PIC, the AVR can
make much tighter assembly and especially C code than the PIC (though I
must admit I haven't worked with PIC18, only PIC16).

I've been wading through a lot of AVR-GCC (free AVR C compiler) listings
lately, and I've actually learned some more efficient assembly
techniques from the compiler than I knew how to do by hand.  It's really
quite good.

Good day!


--
_____________________
Christopher R. Carlen
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Re: Question regarding PIC 18 series performance verses MSP430F149
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... snip ...
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We used to do the equivalent with semiconductors.  However, the
devices were marked "SAT", meaning "selected at test".  Whatever
characteristic that was needed and exceeded manufacturers ratings
was culled from the parts bin before installation.  This sometimes
allows you to build cutting edge instrumentation.

--
Chuck F ( snipped-for-privacy@yahoo.com) ( snipped-for-privacy@worldnet.att.net)
   Available for consulting/temporary embedded and systems.
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Re: Question regarding PIC 18 series performance verses MSP430F149
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<snip>

The MSP is being overclocked at 12MHz, presumably to get the 38us < 40us :)

  If your MSP430 is running 8 bit data variables, then they are not
going to be hugely different.
  Grab the PIC18 tools, port the code, and check it ?

  You could also consider something like the C8051F120, which is
100MHz, and has a 16x16 2 clock mul/Acc - that WILL be a step up
in speed.

-jg


Re: Question regarding PIC 18 series performance verses MSP430F149
Although most responses I've seen favour the MSP, one thing they have
all missed is the gains you can make by hand coding any maths in
assembler. Most C compilers steal your valuable registers from you. On
the MSP registers are the key to high performance. Almost any direct
register operation can be done in a single cycle. Where maths routines
are concerned, except for the very occasional jump, at 2 cycles, the MSP
executes 1 instruction per cycle using registers, and the constant
generators. You need to understand firts how many instructions are
interpreted, anything using a value that can be assigned to a constant
generator (eg BIS #1,foo)
uses the CG register as the source. If foo is also a register it
effectively becomes a register/register operation.

Al

Obelix wrote:

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--
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My apologies for the inconvenience
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