MULTIPLE PROCESSORS OVER MULTI PROCESSOR
One question that has arisen in this field is, "Can you do more with a multiple processor machine with many chips rather than a machine with a single chip that contains multiple processors?" This notion divides into more considerations. Is one more flexible over the other? Which is more cost effective? Which is easier to program? Which can help solve applications in a faster manner? Which one has better hardware? Which is the better controller? Which one has more I/O pins? Which is faster to troubleshoot? Which is more repairable? Are all processors useable? Which is easier to to use in constructing a machine? For these questions and more, let's build a machine and start our comparisons.
For this study, we base our answers to questions by comparing
two actual brand chips, the GA144 by Green Arrays and the Propeller by Parallax. We will create a Propeller machine with the closest number of whole cores to the GA144 chip with 144 cores.
Note: In this comparison, in each category, the processor winner is in parentheses.)
NUMBER OF CORES
Each Propeller has 8 core risc processors. 144 processors is equal to 18 Propellers. So we will compare a one chip machine containing multiple cores to a machine with multiple chips and multiple cores. All chips are different in one way or another. Let's focus on the questions.
INPUT OUTPUT PINS (PROPELLER)
First up, which one has more pins for input output? The Propeller. Each chip has I/O 32 pins. With 18 chips, the machine will have 576 pins. The GA144 has 88 pins with only 25 for I/O.
HARDWARE (GA144)
Which chip has more hardware? The GA144 offers more built in hardware.
FLEXIBILITY (PROPELLER)
Because the design of the Propeller uses software to create hardware, it's more flexible.
NUMBER OF LANGUAGES (PROPELLER)
The GA144 has one language to the Propeller's over 248 languages and variations.
AS A MICROCONTROLLER (PROPELLER)
The Propeller machine as a controller has full access to more I/O pins.
USABLE PROCESSORS (PROPELLER)
Unfortunately
the wiring of the GA144 does not permit all processors to be used at
the same time for some apps. With Propellers, all chips are up and
running, and all cores have access paths.
WHICH IS FASTER? (PROPELLER)
The GA144 would seem faster at first. However, the Propeller is faster when the speed of all 18 Propeller chips and 144 cores are added up.
COST (PROPELLER)
The GA144 is $20 per chip but you are forced to buy a minimum of ten chips. The Propeller is $7.99 each or $143.82 for 18 chips with 144 cores. Because, to get one GA144 you must buy ten, the cost of one GA144 chip will be $200. The Propeller is more cost effective. Also when the Propeller machine has a chip go out, if it ever does, the chip can be replaced and the entire machine is still usable. This makes the Propeller more cost effective because if a single core goes out in the GA144, the entire unit must be replaced.
EASE OF PROGRAMMING (PROPELLER)
The GA144 has only one language - FORTH. The Propeller has options with over 248 languages and their variations. The Propeller is significantly easier to program because it has more programming options, more flexibility and you can choose your favorite language for programming to make things more easy.
MORE REPAIRABLE (PROPELLER)
With the propeller machine, if a chip fails, just unplug it, remove it, and insert a replacement with the handy DIP configuration. With the GA144, the entire chip must be replaced.
TROUBLESHOOTING (GA144)
Which chip is faster to troubleshoot? There's an edge advantage with a single GA144 chip not working. Just throw it away. No need to test other chips.
EASE OF WIRING (GA144)
The GA144 is already permanently wired inside the one chip.
SPECIAL WIRING (PROPELLER)
You can wire in between the chips of processors which is not possible with the GA144.
SUPPORT (PROPELLER)
As we see, and based on the Forums given, the Propeller appears to have ten thousand times more support in terms of the individuals using the product around the world, and with the support offered by Parallax Inc.
CONCLUSION
We looked at 15 comparison points. The propeller wins over the GA144 in eleven points, while the GA144 holds its own in 4 categories. We therefore conclude that for our purposes and for the purpose of this analysis, the Propeller chip, and the technique of using multiple Propellers is superior.
We also believe the GA144 is a very useful, advanced and powerful chip with many potential applications. It may very well win over other processors in other areas not considered in this study.
LINKS
Parallax
http://www.parallax.com/Propeller
Propeller
http://www.parallax.com/Store/Microcontrollers/PropellerChips/tabid/142/List/0/CategoryID/18/Level/a/SortField/0/Default.aspx
GA144
http://www.greenarraychips.com/home/products/
GA144 Brief
http://www.greenarraychips.com/home/documents/greg/GA144.htm