Adding to the info pool...
Upgraded a 2020 iMac 27" i7 from 64GB to 128GB.
In the 64GB configuration, slots 1 and 3 each had a 32GB stick from the same mfg with the same P/N (call this mfg A). Total memory reported as 64GB at a speed of 2667 MHz.
Installed the two new 32GB sticks from a different mfg with their same P/N (call this mfg B) into slots 2 and 4. Total memory reported as 128GB at a speed of 2133 MHz.
Removed the sticks from mfg A and moved the sticks from mfg B into slots 1 and 3. Total memory reported as 64GB at a speed of 2667 MHz.
Reconfigured with mfg A in slots 1 and 2, mfg B in slots 3 and 4. Total memory reported as 128GB at a speed of 2400 MHz.
Didn't try mfg B in slots 1 and 2, mfg A in slots 3 and 4.
Quite the game of whack-a-mole.
Upgraded a 2020 iMac 27" i7 from 64GB to 128GB.
In the 64GB configuration, slots 1 and 3 each had a 32GB stick from the same mfg with the same P/N (call this mfg A). Total memory reported as 64GB at a speed of 2667 MHz.
Installed the two new 32GB sticks from a different mfg with their same P/N (call this mfg B) into slots 2 and 4. Total memory reported as 128GB at a speed of 2133 MHz.
Removed the sticks from mfg A and moved the sticks from mfg B into slots 1 and 3. Total memory reported as 64GB at a speed of 2667 MHz.
Reconfigured with mfg A in slots 1 and 2, mfg B in slots 3 and 4. Total memory reported as 128GB at a speed of 2400 MHz.
Didn't try mfg B in slots 1 and 2, mfg A in slots 3 and 4.
Quite the game of whack-a-mole.
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