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2020 iMac 5K: Memory Bandwidth
Related: 2019 iMac 5K, 2020 iMac 5K, 4K and 5K display, bandwidth, computer display, iMac, iMac 5K, Macs, memory, memory bandwidth, video
MPG tested the 2020 iMac 5K 3.6 GHz Intel Core i9 10-core / 128GB / 2TB / Radeon 5700. Smart move: buy with 8GB memory, then add 64GB or 128GB OWC memory to save a ton on memory cost (same memory as 2019 iMac 5K).
Buy the iMac 5K with 8GB, then upgrade the memory to save about 50%. 128GB is set-and-forget for the life of the machine.
As of January 2020, you can save 78% vs Apple pricing for 128GB memory. That’s not a typo—a savings of about $2000.
If going with only 64GB, there are two different 64GB memory kits from OWC for the 2020 iMac 5K: a 2-module kit and a 4-module kit (less expensive). The 2-module kit costs more because it uses higher-density memory chips, which are more expensive. If going with 64GB, MPG recommends the higher-priced 2-module 64GB kit (2 X 32GB) if there is any potential for later needing 96GB or 128GB*.
This test uses the mt stress command of diglloydTools MemoryTester to evaluate memory bandwidth with a real application using all CPU cores. Not to be confused with memory or CPU specifications—this is the real deal, whatever bandwidth an application actually has available to it combined with what any operating system overhead entails.
Memory bandwidth is especially important for more CPUs; it is important that it be proportional to the CPU computing power. Hence the 2019 Mac Pro with its 28 CPU cores rocks.
The 2020 iMac 5K shows slightly inferior bandwidth to the 2019 iMac 5K. Possibly this is due to macOS Monterey (2020) vs macOS Mojave (2019), but the memory modules themselves could be involved as they are different builds. No module swapping was done to determine whether that hypothesis is correct. The difference is small, only about 6%.
Tested with 128GB OWC memory.