ARM Cortex M0+ CoreMark Ratings
Short answer:


Yes
No


Long answer:

ARM cores have features that each manufacturer may or may not decide to implement (e.g. caches, bus fetch width, FPU, MPU, etc. - of course the availability depend on the type of core e.g. 7xx, 9xx, M0, M0+, M3, M7, etc.). 

Having or not some feature will impact the CPU performance.

The following image is taken from the SAMD21 datasheet. As you can see they decide to implement a fast multiplier and a 32-bit fetch width. This probably allowed the SAMD21 to reach a 2.46 CoreMark/MHz figure.



The datasheet states:


  The SAM D21 devices operate at a maximum frequency of 48MHz and reach 2.46 CoreMark/MHz


(By the way, the SAMD20 also states that it can reach that figure, and not just 2.14).


  The SAM D20 devices operateat a maximum frequency of 48MHz and reach 2.46 CoreMark®/MHz.


If you programmed in ASM two different Cortex M0+, featuring different options (e.g. one has slow multiplier and 16-bit bus instruction fetch width, and the other has a fast multiplier and 32-bit fetch width), then the results would be different. Results would also be different if the test runned on memories with different access times.

Also, the Coremark results, found on the Coremark website, specify the compiler version (and flags used to compile the test). Therefore they are also compiler dependent.