Lpc2000

I'm always very skeptical of the usefulness of these low-level 
performance numbers. They can be useful for seeding the intuition 
engine, but should not be used too much.

These numbers can be useful if you know you have a lot of algorithmic 
work to do (eg. let's say you need to do a bunch of floating point 
calculations on a regular basis).

When it comes to measuring performance of actual running code, a lot 
of other factors come into effect, especially in embedded schearios. 
For example, peripheral access speed: Some devices are very slow at 
bit toggling etc.

You also need to check that the benchmarks match the way you use code. 
For example, the bubble sort. Was it sorting 8-bit or 32-bit values? 
An 8-bitter will chew 8-bit values nicely and do a relatively poor job 
on 32-bit values. On an ARM, the 32-bit stuff will be faster than the 
8-bit stuff.

I'm not sure I believe some of these numbers. For example, the 32-bit 
subtraction should be way faster on an ARM. I hunch that a lot of time 
is being chewed up by looping overheads or saving/storing the values 
(something that is often optimised out in real code) or some other 
time waster.


In short, I subscribe to the adage: Lies, damnd lies and benchmarks.

-- Charles




--- In lpc2000@yahoogroups.com, geno_24@y... wrote:
> 
> I found that FreeRTOS did a performance comparison on several 8-bit 
> and 32-bit parts.  The link is http://www.freertos.org/PC/
> 
> This is a good resource if you are trying to figure out the 
> performance improvement you'll get by going to the LPC2000 from 8-
> bit.  The test parameters are given on the website.
> 
> Does anyone else have these kinds of comparisons or know where I 
> could find them?
> 
> 
> Test	        Philips         Atmel AVR  Microchip   TI
>                 LPC2106        (ATMega323) PIC18F452   MSP430F449
>                 Flash[RAM]
> 16bit addition	9.2µs [7.4µs]   55.2µs     71.6µs   27µs
> 
> 16bit multiply	 9.7µs [8.2µs]	 71.4µs    193µs   72.4µs
> 
> 16bit division	 26.4µs [22µs]	 536µs	   940µs    480µs
> 
> 32bit multiply	10.4µs [8.76µs]	 180µs	   344µs    182µs
> 
> 32bit subtract	 9.1µs [7.6µs]	 88.1µs   76.4µs   57.2µs
> 
> Bubble sort	 432µs [420µs]	 834µs   3.33ms     992µs
> 
> Blk mem move&comp 1.1ms [1.08ms] 7.9ms	 12.4ms    6.75ms
> Cond'l branch to  48µs [46.8µs] 245.6µ  169µs    131µs
> PUSH'ing&POP'ing  43µs          258µs 412µs 314µs
> 
> The PUSH and POP test was performed by pushing and popping a single 
> register at a time. The ARM7 is capable of pushing/poping more than 
> one register in a single instruction.