Apple iMac "Core i3" 3.1 21.5-Inch (Late 2011) Specs

Identifiers: Late 2011 (Edu) - MC978LL/A - iMac12,1 - A1311 - 2496

Identification Differences

Externally, the 21.5-Inch "Mid-2011" and "Late 2011" iMac models all use the A1311 model number but have unique EMC numbers. The 21.5-Inch "Mid-2011" iMac models use the 2428 EMC number, whereas the education-only "Late 2011" iMac uses the 2496 EMC number. These identifiers are all inconveniently located under the "foot" supporting the computer.

In software, all of these models have the same model identifier of iMac12,1, so it only can be used to precisely identify a model when combined with the processor type and speed.

Internal Differences

Internally, the education-only "Late 2011" iMac model is significantly less capable -- with a slower processor with half the number of cores, less memory, less video memory and a smaller hard drive -- compared to the regular "Mid-2011" iMac models.

All of these models support the same 1333 MHz PC3-10600 DDR3 SDRAM SO-DIMMs and have four RAM slots, but the "Mid-2011" models officially support 16 GB of RAM and third-parties have determined that these models actually are capable of supporting 32 GB of RAM. The education-only "Late 2011" model, on the other hand, officially supports only 8 GB of RAM, but actually is capable of supporting 16 GB of RAM.

Other upgrade capabilities may also vary between the lines. As first discovered by site sponsor OWC, the "Mid-2011" models support the 6 Gb/s Serial ATA 3.0 standard for the hard drive/SSD after installing the iMac EFI Update 1.6. The storage drive in the education-only model is believed to also have the same capability, but it is possible that the speed is limited in EFI.

Likewise, all of these models have the processor mounted on an LGA 1155 (H2) processor socket and it is theoretically possible to upgrade the processor to some extent, although doing so is not supported by Apple.

RAM Type: PC3-10600 DDR3 Min. RAM Speed: 1333 MHz

Details: Supports 1333 MHz PC3-10600 DDR3 SO-DIMMs (204-pin).

Standard RAM: 2 GB Maximum RAM: 16 GB*

Details: By default, 2 GB of RAM is installed as one 2 GB SO-DIMM module.

*This model officially supports 8 GB of RAM, but third-parties have discovered that it actually supports 16 GB of RAM.

• About mid page down you will find a video on how to install the RAM: http://www.everymac.com/systems/apple/im...

The process is the same for 2011 21.5" models with EMC 2428 and/or 2429.

You should check sky-writer.com/advancedwriters-review/ out for some help. It does have a process for 2011 models with EMC 2428 but overall, it is the same thing with a bit more restrictions to it

Seems there is conflicting advice as to what might be the cause. 1. static 2. GROUNDWORK electricity supply issues 3. Sockets not earthed correctly. Or it could be the machine is at fault because the aluminium casing is more likely to conduct electricity.

I have already carried out the two tests you mentioned. No fault was found. Plus the Imac was the only electrical equipment on in the room. There was no other machine it could have come from?

Seems there is conflicting advice as to what might be the cause. 1. static 2. GROUNDWORK electricity supply issues 3. Sockets not earthed correctly. Or it could be the machine is at fault because the aluminium casing is more likely to conduct electricity.

Seems there is conflicting advice as to what might be the cause. 1. static 2. GROUNDWORK electricity supply issues 3. Sockets not earthed correctly. Or it could be the machine is at fault because the aluminium casing is more likely to conduct electricity.