One thing that has me bugged about the M marketing

[GIR]

Okay now BMW marketing is doing their thing, which has been pretty effective. One thing that has me bothered is that they're saying they have 32bit Motorola ARM processors for their ECU.

This is kinda bullshit in my eyes. Why? The ECU purely operatos on data supplied to it by sensors around the car and engine. Now the Motorola processors have 16 10bit ADC's (Analog to Digital Converters), these are needed to translate the values of the sensors into binary data the processors understand. I'm assuming that BMW isn't using the onboard ADC's but have ADC's on the sensors themselves, this is actually cheaper and easier todo as it safes space and wiring.

Even then the max they could achive is around 12 to 16bit. There are 18 and even 20bit ADC's around but those are so huge that they wouldn't be practical at all. Mostly those are used in steady setups like Sonar equipment and such.

Now lets assume for a momment that BMW is using 16bit ADC's (I truely do not know what they're using) this would mean using 32bit processors is overkill! Imagine you have to transport something in a container twice the size, that's what's happening. They have a processor which can process 32bit's at once but they only supply it with 16bits.

An automatic response would be (for a person who doesn't know) that the the processor could do 2 16bit operations in the time it could do 1 32bit operation. But this is not the case. When the processor is supplied with 16bit data it just fills the missing 16bit with 0 and then performs the operation.

The calculations performed by the ECU are very taxing. mostly it's floating point operations which take alot of time to execute. A 32bit processor would be very usefull there, but then again there are other options BMW could've used instead of ARM processors which are more suitable for this situation.

I really do not know why BMW marketing is throwing this around the net because if I had to use 3 200MHz ARM processors it would be something I would be ashamed of. It's a sign of incompetance or being just too lazy todo proper sollution.

200MHz is not something you just throw into something without concidering the consequences. everything above 40MHz becomes very sensitive for external influinces and starts to influince things around it. I'm just hoping BMW designed those ECU'd properly and those ECU's don't start to fail.

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Hallo GIR,

 

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[bleh]

the only real benefit to having more bits is to provide for more registers. being operators or memory addresses. but as mentioned, this requires more work from the processor. i dont think its a good idea since most ecus dont have the requisite of having a higher level of computing. also i have already heard of a few of bmw's errors with electronics, making them a better candidate for failure with complexity. i agree with you GIR as i proudly wave my BS flag.

ok the easy to read version, non computer science version:

having a processor with more bits allows for either more things(operations, functions) the processor can do or more values it can store. the problem with this, as GIR mentioned is that a clock cylce will be longer with having longer names for everything. forcing the hardware to perform at a higher level. this is totally unnecisary. bmw has already screwed some things up with their ecus so this is really a bad idea. i agree with GIR and think bmw is dumb for doing this.

[GIR]

For the price of 3 Motorola ARM processors they could've used several dsPIC's, which are basicly programmable DSP's (Digital Signal Processors).

As the name sais they are processors optimized for processing signals. A regular processor isn't all that good in doing floating point operations. Everybody who has a computer will recognize terms like co-processor, MMX, SSEE, 3DNOW and even 3D graphics cards from nVidia and ATI. These are aditions to normal desktop computers which help the regular processor with operations that would ussualy take a long time for the regular processor todo.

A DSP is specificaly optimized todo mathematical equations. a signal comes in a operation is performed and a signal is sent out. it's almost instantanious compared to the Motorola processors.

Personally I favor the Microchip dsPIC's:

http://www.microchip.com/stellent/idcplg?IdcService=SS_GET_PAGE&nodeId=75

These are more then suitable todo the job and will probably give more performance (calculation wise) and cost a whole lot less.

[LateNightCable]

Okay, only true techno mirochip geeks would make a case out of this one, or even be peeved over it. I don't think their ECU's are one of BMW's major selling points anyway, because such matters would bore the life out of the average buyer. The average person wants to hear about 0-60 and horsepower per liter, not what the ECU is packing and how it does it. But if there is a 32bit processor in the car, regardless of the sensors, it's legit to say you have it, right?

But my guess is perhaps they have a good discount deal going with Motorola. The reason for this is because Motorola now supplies all of BMW's in-car communication needs, such as the newly available integrated Bluetooth feature, which hooks up to BMW's own iDrive.

Now if you get married, you're going to eat your wife's meatloaf and pack it in your lunch box too. Even if your former girlfriend's recipe tastes better. Marriage can make you do funny things. - Funny things can lead you to marriage too.

[Thunf]

About chips and dipps there is always stupid marketing involved! I read about "digital prosessed Bass Boost" on a pair of headphones! Uuuu, impressive eh? It looks cool, "digital bla bla..." only a simple DSP threated signal is marketed like that, nothing is wrong but it's kind of crazy..

"horsepower per liter"? why is that all that matters for some? It's a dilemma I don't understand.

V8 479 hp Mercedes E55 does 12.9 l/100 km, 87.5 hp/litre, kerb weight 1835 kg.

compare:

V8 490 hp Ferrari F430 does 15.27 l/100 km, 115 hp/litre, kerb weight: 1450 kg

V8 626 hp Mercedes SLR McLaren does 14.8 l/100 km, 115 hp/litre, kerb weight 1768 kg.

Ok, the Ferrari is lighter - that should make better consumption, no supercharging - but still throws wasteheat from the car as hell! But it does make more hp/litre. Fantastic!

I've compared it to M5 before too, but that has a V10 101hp/litre. It makes 14.8 l/100 km, tssk! even the same class as the 120 hp stronger SLR!

NA engines have it's disadvantages and advatages yes. It's really strange that some people only think engine efficiency in hp/litre.... let's see how consumption /litre look like!

E55: 2.37 l/100km per litre engine capasity

F430: 3.55 l/100km per litre

SLR: 2.72 l/100km per litre

M5: 2.96 l/100km per litre

Performance cars ofcourse can't be compared with ordinary cars in terms of fuelconsumption, but the figures here makes a hint that throwing a compressor on like 'bolting on' your car don't make these figures! Fantastic figures about hp/litre alone is not worth a damn thing! If the next car I'd buy would be 7 litres capacity and 40 hp/litre still lightweight good handling I'd take that if consumption would be lower than comparable car with 200 hp/litre! Just my 2 cents..

[bleh]

hp/liter is just another bench mark. being able to extract a certain amount of power from a certain sized engine. it is worthy of its own thread