Chosen Solution
Hi, I have just upgraded my iMac by adding 16GB (2x8GB) to the pristine 8GB (2x4GB). Since I know, but I may be wrong, that modules should be coupled, how do I have to do it? By now I have made a try, putting physically close, in the 4 available trays, similar modules (4GB with 4GB, 8GB with 8GB). This is the configuration I got from system info (RAM modules coupled in the same bank) BANK0/DIMM0 8GB BANK1/DIMM0 4GB BANK0/DIMM1 8GB BANK1/DIMM1 4GB Is this correct, or should I insert them physically alternated, so they I have the same modules coupled in the same DIMM? Thanks for your help Francesco
After reading contradictory answers, I decided to make some tests to determine what the correct way to add (2 x 8 GB) RAM to existing (2 x 4 GB) RAM. And this are the results I found. Tested on iMac (27-inch Mid 2011) Intel Core i7 - 3.4 Ghz with High Sierra: With the following configuration from System Information / Memory (by BANK): *** BANK 0/DIMM0: 4 GB - DDR3 - 1333 Mhz BANK 1/DIMM0: 8 GB - DDR3 - 1333 Mhz BANK 0/DIMM1: 4 GB - DDR3 - 1333 Mhz BANK 1/DIMM1: 8 GB - DDR3 - 1333 Mhz Geekbench 4 shows and memory bandwitdh at 8.76 GB/sec for Single-Core and 8.61 GB/sec for Multi-Core (Full results at : https://browser.geekbench.com/v4/cpu/101…) With the following configuration System Information / Memory (by DIMM): *** BANK 0/DIMM0: 4 GB - DDR3 - 1333 Mhz BANK 1/DIMM0: 4 GB - DDR3 - 1333 Mhz BANK 0/DIMM1: 8 GB - DDR3 - 1333 Mhz BANK 1/DIMM1: 8 GB - DDR3 - 1333 Mhz Geekbench 4 shows and memory bandwitdh at 15.4 GB/sec for Single-Core and 16.6 GB/sec for Multi-Core (Full results at : https://browser.geekbench.com/v4/cpu/101…) The good configuration to exploit the Dual Channel to get the best performance is “by DIMM” meaning to have same RAM sizes in same DIMM number. Daniel
Is possible that same RAM sizes should be in DIMMs and not in BANKs? Maybe apple just call them differently. Because here is screenshot how looks 12GB from factory in iMac.
Sorry, I may be wrong, but I was told to use the same amount of RAM/memory in each channel/bank, 12 in each. the pristine configuration (4GB Slot 1 and 4GB Slot 3 - iMac Late 2015) would validate this (regarding to dual channel). BANK 0/DIMM0: Größe: 4 GB Typ: DDR3 Geschwindigkeit: 1867 MHz Status: OK BANK 0/DIMM1: Größe: 8 GB Typ: DDR3 Geschwindigkeit: 1867 MHz Status: OK BANK 1/DIMM0: Größe: 4 GB Typ: DDR3 Geschwindigkeit: 1867 MHz Status: OK BANK 1/DIMM1: Größe: 8 GB Typ: DDR3 Geschwindigkeit: 1867 MHz Status: OK
Correct! You want the SAME sized modules within the BANK. Sadly, you have different sized modules within the BANK: BANK0/DIMM0 has a 4GBBANK0/DIMM1 has a 8GB Where you want: BANK0/DIMM0 will have a 4GBBANK0/DIMM1 will have a 4GB The other bank would be setup: BANK1/DIMM0 will have a 8GBBANK1/DIMM1 will have a 8GB Or you could go the other way were Bank 0 has the larger modules. Note: The number after the word BANK thats the bank number NOT the DIMM number.
