2017 iMac machines use DDR4 memory

Apple released a refresh to the iMac lineup June 5 2017.

The iMac machines are noted for their all in one desktop design with high-quality ‘Retina’ LCD screens (5K resolution on the 27 inch, 4K resolution on the 21.5 inch).  These latest iMacs use the Intel Kaby Lake series processors, which are faster and cooler than their predecessors.

The biggest change on the memory front is that they have switched to DDR4 memory from the earlier DDR3.

As we have seen before, the iMac 21.5 inch models are not upgradeable, you can choose a pre-installed RAM amount from the factory only (Configurable to 16 GB, or to 32 GB on the top 3.4GHz model). These machines are glued together, and are not accessible to someone other than a technician.

The new 27 inch machines have a 4-SODIMM slot configuration like earlier models, and the 3.6 GHz and 3.8 GHz machines can go to 64 GB RAM with four DDR4 16 GB SODIMM modules.  The modules are specified at 2400 MHz (PC4-19600), which is one step up from the entry level 2133 MHz that most DDR4 machines use.

One puzzle is that the 27 inch 3.4 GHz i5 machine is limited to 32 GB total RAM in the Apple Technical Specifications.  This may be a hardware limitation, or purely a marketing decision on Apple’s part.  There’s no technical reason the memory controller in the Kaby Lake CPU can’t handle 64 GB.

Canadaram.com stocks DDR4  memory for the iMac 2017 models  http://canadaram.com/apple_imac_intel.htm#iMac2017

Apple’s other claims for the new machines include faster graphic performance with Radeon Pro 500-series discrete graphic chips, and faster performing SSD drives (claiming 50% faster). Keep in mind that this doesn’t mean the machine will run 50% faster, these figures are a bit of specsmanship – raw theoretical bandwidth numbers are several steps removed from real-world performance improvement.

All of the 27 inch models come standard Quadcore i5 CPUs and with 1TB or 2TB Fusion drives (a hybrid of a small SSD and a larger spinning hard drive, ‘spliced’ together by the operating system).  Fusion drive sets are faster than standard hard drives but slower than straight SSD drives. Apple is choosing this approach to bridge between the high storage demands of media (all those iTunes Movies and Photos libraries) and the high cost of large SSD drives.

The standard configurations can be customized with larger Fusion drives, or 256GB, 512GB or 1TB SSD drives, and the 3.6GHz and 3.8 GHz models with Quadcore i7 processors (note that 8 core i7s are not offered)

Apple claims that their latest Retina screens are brighter and have more accurate color that the previous models, partially due to the use of red-green LED backlighting.

The iMacs come standard with two Thunderbolt 3 ports, which share the same connector form factor as USB C.  With the correct Thunderbolt 3 or USB 3.1 peripherals, this enables high speed storage as well as connection of multiple displays. Owners of Thunderbolt 1 and 2 peripherals will have to get a TB3 to TB2 converter. The iMacs retain 4 standard USB 3.0 A-Type ports for peripherals like keyboard, mice and printers.

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