- Method 1:
Look at the front for the infrared (IR) sensor. If there is a small round IR window next to the left speaker, it’s a Rev A or Rev B.
If there is no IR window, it’s a Rev C or Rev D.
Here is how the front left of a Rev C or Rev D model would look like, with no IR sensor present.
- Method 2 (Know Exact Revision):
Check the blue circle sticker on the bottom of the iMac.
- If the sticker lists specs like CPU and RAM but does NOT mention the graphics card (ATI Rage IIc), it’s a Rev A.
- If the sticker lists specs and includes “ATI Rage Pro,” it’s a Rev B.
- If the sticker is present but does not have any specs written, it’s a Rev C or Rev D as shown below
To tell Rev C and Rev D apart, check the CPU speed by going to system information in the OS or looking up the serial number: Rev C runs at 266 MHz, Rev D at 333 MHz.)
Method 3: Check if there is a mezzanine slot on the ports (right side of the iMac)
Rev A and Rev B models have a mezzanine slot
Rev C and Rev D models do not have a mezzanine slot as seen here.
Fun Fact: Apple insisted on not using the mezzanine slot but third parties reverse engineered it and made SCSI port expansions. It is still a mystery to this day as to why Apple included it.
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