Relative IPC and efficiency of some Intel CPUs in Cinebench R15

[porina]

Consider this pre-testing to a wider IPC test. I ran Cinebench R15 in various configurations on 3 CPUs representing 3 different generations.

• 12100F - Alder Lake, Intel 7 (formerly 10 Enhanced SuperFin)
• 11700k - Rocket Lake, 14nm
• 7980XE - Skylake-X, 14nm

Rocket Lake was the first desktop generation past Skylake architecture even though it was still made on 14nm process, and Alder Lake finally took desktop beyond 14nm nodes.

 

Why use Cinebench R15? Mainly because it is well known, and as older software it does not make use of AVX instructions so takes away an element of complication. It is known to not be much affected by memory performance which is good if I'm focusing on the CPU cores itself. I note the score, reported CPU power consumption, and where possible the CPU clock. In some scenarios with a power limit, the clock varied too much to get a good value. Skylake-X here should be near enough a substitute for regular Skylake and derivatives (Kaby Lake, Coffee Lake, Comet Lake).

 

Note this is "quick testing" and I didn't try to eliminate all variables and check of repeatability beyond doing a minimum of 2 runs each.

 

Relative performance (IPC best case):

Skylake-X: 52.2 points/core/GHz

Rocket Lake: 63.3 points/core/GHz, +21% relative to SKX

Alder Lake: 72.7 points/core/GHz, +39% relative to SKX, +15% relative to RKL

 

Relative efficiency:

This is where it gets really complicated. It depends on where on the efficiency curve you compare, and these are wildly differing CPU configurations. I used a metric of points/W for comparison.

 

7980XE unlimited (188W): 16.6 points/W

7980XE turbo off (117W): 20.9 points/W

11700k unlimited (183W): 12.7 points/W

11700k turbo off (88W): 20.4 points/W

11700k 45W limit: 22.5 points/W

11700k 25W limit: 23.1 points/W

12100F unlimited (56W): 20.3 points/W

12100F 45W limit: 23.9 points/W

12100F 25W limit: 30.2 points/W

 

I decided against testing the 7980XE at lower powers since it was reporting around 45W usage at idle! 

 

We still have different core configurations. I tried adjusting the 11700k further, running it with only 4 cores enabled (4c8t), and also running it with all cores and HT off (8c8t).

 

11700k 4 cores 8 threads

125W limit: 10.1 points/W

45W limit: 18.3 points/W (Alder Lake 30% more efficient)

25W limit: 18.6 points/W (Alder Lake 62% more efficient)

As generally expected, this is much worse than running with 8 cores. While each core has more power available, it runs in a less efficient area. Alder Lake does seem to scale better at lower powers. Note although is is 4 core vs 4 core, by disabling 4 cores of Rocket Lake it may not scale exactly. Intel did not make a 4 core Rocket Lake.

 

11700k 8 cores 8 threads (HT off)

Unlimited (159W): 11.1 points/W

45W limit: 18.5 points/W

Cinebench R15 is on the higher end of HT scaling workloads. For a 45W power limit, it is doing 18% less work than with HT on. While it was not a part of my testing this time, previously I've seen typically around 30% more throughput at the same clock with HT, implying the difference here is due to the extra power consumed by HT. Arrow Lake is rumoured to not have HT so it will be interesting to see how that goes overall.

 

Overall we do see a bit more efficiency from the newer process, especially at lower powers. There is also a clear improvement in IPC between the generations. Of course, this is very limited in only looking at Cinebench R15, and I hope to expand this to wider workloads over time.