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Tesla lowers Model 3 range estimates in Europe due to extra power consumption of AMD Ryzen processor

diamond.g

Active Member
Nov 5, 2015
2,509
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Moyock, NC
I think you're both wrong. TDP is the indefinitely sustained power draw a chip can handle and the power draw one can expect when operating at the rated speed on all cores. (The rated speed is based on TDP.) In a way it's sort of like an average as it can burst higher for short periods. So if you have a 45W n-core chip rated at 2GHz and run all n cores with a full workload at 2GHz it should draw around 45W. Most modern CPUs can burst higher than the rated speeds for short periods or if some cores are idled/shut down.

Obviously, as some have pointed out it is extremely unlikely that a Tesla would be running either of these CPUs at max TDP all the time unless Tesla's engineers are particularly stupid.
In this case the CPU they are using isn't as fancy as the later variants, boost clocks work weirdly on pre Zen 2 (which this is) CPU's.
I've pointed it out before, but for a very slow drive cycle that drags in for dozens of hours (the EU cycles might be), while having low average energy demand (like the UDDS cycle), even 45W can add up to a significant amount and result in multiple miles of range difference.

Everyone here also seems to be forgetting the Navi 23 discrete graphics. That has a TDP of 65-90W depending on model and as far as I can find, the previous Atom infotainment system didn't have an analog to it, so this is completely new power demand. It would be interesting to see what the idle or low demand power draw of the new GPU is.
Assuming all the cars are getting the GPU daughtercard (and not just the S/X).
 
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It only takes a difference of approx 50 watts could change the range by 7 miles.
As I know, it's false. WLTP range is based on 13-16 kWh average consumption. It means 13000W-16000W average consumption by the car. If you want 3.5% range drop, you need to increase the consumption by at least 455W. It's not just an Atom to Ryzen 15->45W (30W increase), and also not just the extra Navi 23 GPU 0->160W (160W increase) maximal consumption, it is much more.. Something else is happening.. Not just "the Ryzen". For example, the FSD computer is replaced also, or the range drop is only theoretical, like Tesla measures the WLTP / EPA differently from now on.

Is there anyone, who knows the answer? :)
 

stopcrazypp

Well-Known Member
Dec 8, 2007
11,991
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As I know, it's false. WLTP range is based on 13-16 kWh average consumption. It means 13000W-16000W average consumption by the car. If you want 3.5% range drop, you need to increase the consumption by at least 455W. It's not just an Atom to Ryzen 15->45W (30W increase), and also not just the extra Navi 23 GPU 0->160W (160W increase) maximal consumption, it is much more.. Something else is happening.. Not just "the Ryzen". For example, the FSD computer is replaced also, or the range drop is only theoretical, like Tesla measures the WLTP / EPA differently from now on.

Is there anyone, who knows the answer? :)
Did you mean 13-16 kW? Where did you get those numbers? Do you have a link?

EPA is much lower:
UDDS ~3200W
Highway ~8400W
FTP ~5300W
There's still other correction factors that changes this, but from the pure test numbers, the cycles don't actually consume that much power on average, so a continuous power draw may be more significant than you may think.
Tesla lowers Model 3 range estimates in Europe due to extra power consumption of AMD Ryzen processor

Just some quick math:
EPA shows max usable is 82kWh for Model 3 LR:
Previous WLTP range was 614 km.
Tesla Model 3 Long Range Dual Motor
WLTP cycle used would be Class 3B (larger vehicles with Vmax greater than 120km/h) and average speed there is 23266m/1800s = 12.93 m/s = 46.55 km/h
Emission Test Cycles: WLTC
That means the test would take 614km/(46.55km/h) = 13.2 hours
82kWh/13.2h = 6.2 kW

That matches the ball park of the consumption on the EPA test, so makes sense.

And to finish the math, 12km (claimed difference)/614km is 2%, 2% of 6.2kW is around 120W. That's more than from the Ryzen APU alone, but if you add in the Navi GPU (assuming it's true it's discrete, which from what I can find there is no analog in the Atom computers) it's not out of the realm of possibility.
 
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And to finish the math, 12km (claimed difference)/614km is 2%, 2% of 6.2kW is around 120W. That's more than from the Ryzen APU alone, but if you add in the Navi GPU (assuming it's true it's discrete, which from what I can find there is no analog in the Atom computers) it's not out of the realm of possibility.

Given what I'd assume is additional thermals, and subsequently, extra cooling requirements for the new MCU, I wonder how much that affects total consumption, if at all[?]
 
Did you mean 13-16 kW? Where did you get those numbers? Do you have a link?

EPA is much lower:
UDDS ~3200W
Highway ~8400W
FTP ~5300W
There's still other correction factors that changes this, but from the pure test numbers, the cycles don't actually consume that much power on average, so a continuous power draw may be more significant than you may think.
Tesla lowers Model 3 range estimates in Europe due to extra power consumption of AMD Ryzen processor

Just some quick math:
EPA shows max usable is 82kWh for Model 3 LR:
Previous WLTP range was 614 km.
Tesla Model 3 Long Range Dual Motor
WLTP cycle used would be Class 3B (larger vehicles with Vmax greater than 120km/h) and average speed there is 23266m/1800s = 12.93 m/s = 46.55 km/h
Emission Test Cycles: WLTC
That means the test would take 614km/(46.55km/h) = 13.2 hours
82kWh/13.2h = 6.2 kW

That matches the ball park of the consumption on the EPA test, so makes sense.

And to finish the math, 12km (claimed difference)/614km is 2%, 2% of 6.2kW is around 120W. That's more than from the Ryzen APU alone, but if you add in the Navi GPU (assuming it's true it's discrete, which from what I can find there is no analog in the Atom computers) it's not out of the realm of possibility.

I do mean kWh / 100km WLTP consumption, you can average it out.

a.) I've seen many different values, thats why I wrote 13-16.. for example this site shows the same magnitude:


WLTP Ratings (TEL)​

Range614 km
Rated Consumption147 Wh/km
Vehicle Consumption122 Wh/km


b.) But if you do the math about WLTP range and battery, you get the same scale: 614 km from the 82kWh battery: 13,35 kWh/100km..

c.) If you just think about it: an EV uses 10-35 kWh (35 is for SUV cars going fast) between city usage and motorway speeds / 100 km.

(Anyway, new Model 3 Ryzen owners say the range stays the same, doesn't matter if Atom / Ryzen with the same 60kWh battery.)
 
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stopcrazypp

Well-Known Member
Dec 8, 2007
11,991
7,747
I do mean kWh / 100km WLTP consumption, you can average it out.

a.) I've seen many different values, thats why I wrote 13-16.. for example this site shows the same magnitude:


WLTP Ratings (TEL)​

Range614 km
Rated Consumption147 Wh/km
Vehicle Consumption122 Wh/km


b.) But if you do the math about WLTP range and battery, you get the same scale: 614 km from the 82kWh battery: 13,35 kWh/100km..
Ok, I see the mistake you are making. You are assuming the car is going on average 100 km/h. That is the only way you can directly use the numbers to get a kW number. Basically you are doing the following math implicitly: 13.35kWh/100km * 100km/h = 13.35 kW.

The problem is the average speed of the WLTP cycle is much lower than that! The car is travelling on average 46.55 km/h (keep in mind you must include also the parts of the cycle where the car is stopped or going very slow). The computer is basically a parasitic drain that constantly runs, so the slower the car goes on average, the higher the impact.
c.) If you just think about it: an EV uses 10-35 kWh (35 is for SUV cars going fast) between city usage and motorway speeds / 100 km.

(Anyway, new Model 3 Ryzen owners say the range stays the same, doesn't matter if Atom / Ryzen with the same 60kWh battery.)
But this thread is not discussing the real world impact. I don't think anyone is disputing it's very little if any (even 2% really is nothing vs other real world variables). This is discussing if it is plausible for there to be a 2% impact on the car on a WLTP cycle. Both your numbers and mine show that is plausible, given that only works out to 120W. This is assuming talking about OP with Model 3 LR having 12 km (7 miles) lower range vs 614 km originally.
 
Ok, I see the mistake you are making. You are assuming the car is going on average 100 km/h. That is the only way you can directly use the numbers to get a kW number. Basically you are doing the following math implicitly: 13.35kWh/100km * 100km/h = 13.35 kW.

The problem is the average speed of the WLTP cycle is much lower than that! The car is travelling on average 46.55 km/h (keep in mind you must include also the parts of the cycle where the car is stopped or going very slow). The computer is basically a parasitic drain that constantly runs, so the slower the car goes on average, the higher the impact.

But this thread is not discussing the real world impact. I don't think anyone is disputing it's very little if any (even 2% really is nothing vs other real world variables). This is discussing if it is plausible for there to be a 2% impact on the car on a WLTP cycle. Both your numbers and mine show that is plausible, given that only works out to 120W. This is assuming talking about OP with Model 3 LR having 12 km (7 miles) lower range vs 614 km originally.
Thanks for the explanation, I will think about that! :)
 

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