72-Pin SIMMs: Which Macs Support Industry Standard (3/94)

All desktop Macintosh models introduced since February 1993 use 72-pin SIMM slots for their RAM. This type of SIMM is considered an industry standard, and is widely available for other brands of computers.

However, the specification for using these SIMMs with Macintosh computers omits the ninth parity bit, which is part of the so-called "industry standard." Will these SIMMs still work when installed in the new Macintosh models?

The ninth parity bit in 72-pin SIMMs installed in Macintosh slots is ignored and should not present any problems. However, it is always best to test a type of SIMM carefully in all banks in any Macintosh models you intend to use.

The SIMMs that work in Macintosh models supporting 72-pin SIMMs are considered industry standard 72-pin SIMMs, but not all "industry standard" SIMMs are guaranteed to work in these Macintosh systems. In other words, these Macintosh models might require the "higher" quality SIMMs that meet industry standards. When purchasing SIMMs, be sure you get 72-pin fast-paged mode with 60ns access time or faster (80ns for the Macintosh LC III).

Be aware that Apple does not support composite SIMMs for the 72-pin SIMM form factor. (Composite SIMMs are SIMMs manufactured using a smaller or older memory technology. An example of this would be a 16MB SIMM made of rows of 4MB chips -- basically a 16MB SIMM made of four 4MB SIMMs on one board. Composite SIMMs are never recommended for use in Apple computers.)

Article Change History:
25 March 1994 - Retitled and edited article.

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