Question Discussion over P-core and E-core vs AMDs regular vs C-core

[Hulk]

Sadly, that slide is misleading. It already takes into account, that for the same MT performance more Zen4c cores are used and that they clock lower than a comparable Zen4 SKU. Looking at the V/f curve, Zen4c is quite disappointing IMHO.

I fully expect AMD to specialize their two cores more in the coming generations, where the c-cores show real efficiency improvements in terms of Work per Joule. This might only be the case for Integer.
All in all, in the client space the heterogenous approach makes sense to me due to Amdahl's law. Server space is different, because there it does not apply in the same way. There, many smaller cores might become the standard while big cores might only be used for special workloads and applications that get licensed by core count usage.

These types of promotional charts are generally terrible but this one sets a new low in my opinion. I mean we expect a lack of numerical values, no scale, and other missing parameters, but this one really shows nothing except efficiency is "better" and frequency is "lower." Oh yeah, and size is "smaller." Absolutely no useful information like what is the difference in frequency? How does efficiency compare at various iso power and iso frequency points?

So according to this chart Zen 4C is half the area of Zen 4, is that correct?

Frequency for 4C should be about 35% lower, correct?

Power efficiency about 50% better at some frequency/workload, correct?

If 4C is half the area, and 50% more efficient then that is quite impressive so I would expect AMD to just come out and state those numbers.

 

[Abwx]

Sadly, that slide is misleading. It already takes into account, that for the same MT performance more Zen4c cores are used and that they clock lower than a comparable Zen4 SKU. Looking at the V/f curve, Zen4c is quite disappointing IMHO.

I fully expect AMD to specialize their two cores more in the coming generations, where the c-cores show real efficiency improvements in terms of Work per Joule. This might only be the case for Integer.
All in all, in the client space the heterogenous approach makes sense to me due to Amdahl's law. Server space is different, because there it does not apply in the same way. There, many smaller cores might become the standard while big cores might only be used for special workloads and applications that get licensed by core count usage.

You didnt read the thing accurately, it cant clock as high but has higher efficency at same frequency.

 

[jpiniero]

You didnt read the thing accurately, it cant clock as high but has higher efficency at same frequency.

That's not what the chart says. Breakeven point is at 17.5 W although it's close enough that it's well worth the area savings.

 

[Abwx]

That's not what the chart says. Breakeven point is at 17.5 W although it's close enough that it's well worth the area savings.

PHX2 is a compromise because mixing Zen 4 and Zen 4C yield something that is not optimal, FI the voltage must be aligned with Zen 4 even if Zen 4C was to require a slightly lower voltage.

For an accurate comparison one has to check by disabling the 2 regular cores, that s what Phoronix wanted to do but so far he said that the regular cores couldnt be disabled as of now.

 

[BorisTheBlade82]

You didnt read the thing accurately, it cant clock as high but has higher efficency at same frequency.

As I said before, the V/f curve shows no difference to write home about - but that does not tell the whole story. The comparison of PHX2 vs. 6c Zen4 is almost in the margin of error. So far I have not seen any efficiency comparisons of Bergamo vs. Genoa with equal core count and frequency. If you have any, I would be very thankful. The Phoronix review only showed what everybody knows: More cores at the same TDP give better efficiency due to clocking slower.

Compare this to Apple: Their small cores are significantly more efficient in terms of more work per Joule. That is what I had hoped for Zen4c as well. and that is what I hope for future generations.

 

[Abwx]

The comparison of PHX2 vs. 6c Zen4 is almost in the margin of error.

You re looking the wrong way, comparison should be done at same throughput, that is at same frequency, so look at the horizontal delta between the two chips, 12W are required by PHX1 to match PHX2@10W, 20% better perf/Watt at same throughput is hardly in the margin of error, and that s with two regular Zen 4 cores bringing down the chip efficency.

 

[Saylick]

Aptly timed C&C article on Zen 4 vs Zen 4c cores with their review of the ASUS ROG Ally:

AMD’s Mild Hybrid Strategy: Ryzen Z1 in ASUS’s ROG Ally

Editor’s Note: ASUS sent us the ROG Ally sample – our first review sample from a company – in order to test the Ryzen Z1 SOC inside the device. So a massive thank you to them! CPU…

chipsandcheese.com

 

[BorisTheBlade82]

You re looking the wrong way, comparison should be done at same throughput, that is at same frequency, so look at the horizontal delta between the two chips, 12W are required by PHX1 to match PHX2@10W, 20% better perf/Watt at same throughput is hardly in the margin of error, and that s with two regular Zen 4 cores bringing down the chip efficency.

Oh well, I had several long and close looks at this slide
And sadly, the ISO-throughput comparison does not show 20%, but more like 13-15% - at least the region where the horizontal line applied by myself crosses Zen4 looks more like around 11.4w to me.

But I really do not want to be nit-picky. Yes, Zen4c seems a bit more power efficient, you are right in that. So let's just say, that I am a little disappointed because I had expected more.

 

[FlameTail]

HUGE: Intel-P, Apple-P, AMD Zen, Oryon Phoenix
BIG: Cortex X, AMD Zen C
Medium: Cortex A7xx, Apple-E, Intel-E
little: Cortex A5xx

How accurate is this classification?