![]() Or put another way, it takes 52% longer with 28 CPU cores than with 56 (virtual) CPU cores. Remarkably, and unlike what I’ve seen in most all software, these additional virtual CPU cores drop run time 34% from 602 seconds to 397 seconds. The CPU cores are real CPU cores out to 28, then the additional cores are virtual CPU cores (one more per real core), for a total of 56 CPU cores. The difference is not large (about 5%), but it is very real.įrom 17 cores onward, the 28-core Xeon takes the lead. Probably because as laggards, they add overhead and create choke points by being laggards. The graphs shows us that M1 Ultra efficiency cores degrade performance (core count 17/18/19/20 vs 16). And yet, other compelling tests show that the M1 Ultra does NOT downlock. Otherwise, we should see a steady divergence with the Mac Pro as its CPU downclocks-but we do not see that. Most striking is that with up to 16 CPU cores, the Xeon and the M1 Ultra hardly differ up to 16 CPU cores! Which implies that the M1 Ultra seemingly also downclocks its CPU cores as more cores are used (Apple takes pains to not mention clock speed at all in marketing the chip). It never works quite that well barring very specialized computing tasks and specialized hardware, and even that has its limits. Scalability should be evaluated proportional to the number of CPU core, e.g., twice as many cores ideally would run 2X faster. ![]() But there is no obvious way to correct for those differences, and so the graph is shown cores-vs-cores. ![]() In a nutshell then, the number of cores is not directly comparable given the variable clock speed of the Xeon and the efficiency cores of the M1 Ultra. With only 1 or 2 cores in use, the Xeon can hit higher clock rates (4.6 Ghz?), and then as more and more cores are used, the clock speed drops all the way down to a lazy 2.5 GHz. But perhaps there is another explanation. But the Xeon upclocks itself as high as 4.6 GHz and downclocks itself all the way to 2.5 GHz as more cores are used.ĭoes the M1 Ultra maintain its 3.6GHz clock speed even when all 16 performance cores are in use ? The graph suggests that it does not, since it runs almost identically in speed to the 28-core Xeon, whose clock speed is steadily dropping as more cores come into use. This graph is misleading in a certain sense: both the M1 Ultra and 28-core Xeon CPUs run at a nominal 3.6 GHz. Still, Zerene Stacker does have serialization points and this limits the number of cores which are useful. However, the massive memory bandwidth of the M1 Ultra means that memory bandwidth is a minimal issue, and there is no I/O with Zerene Stacker. Often there are choke points ("serialization") that prevent more than one or a few CPU cores from being used simultaneously along with contention for resources (memory bandwidth, I/O, shared data structures etc). Amdahl’s law definitely applies to Zerene Stacker. This graph is an outstanding demonstration of the diminishing returns of more CPU cores vs real-world computing problems. Zerene Stacker version 1.0.4 T-0715-beta. See for example Nikon D850 'Focus Shift shooting' feature for Easy Focus Stacking. If below are out of date: view current Mac wishlist and all current OWC wishlists.ĬLICK TO VIEW: Apple Mac Studio at B&H PhotoĬLICK TO VIEW: Thunderbolt and Related Accessories Results This page looks at focus stacking speed with Zerene Stacker vs number of CPU cores used. ![]() See the discussion of Zerene Stacker for focus stacking on the comparison page. ![]()
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