Low End Mac Reader Specials
Apple broke the envelope with the IIfx: the 40 MHz CPU on a 40 MHz bus left everything else in the dust. Because it needed faster memory than any previous Mac, it used a special 64-pin SIMM. It was the first Mac to ship with 4 MB of RAM.
The greatest drawback in upgrading RAM in the IIfx is the location of the SIMM sockets. You need to remove the entire drive support assembly (holds floppy and hard drives) to access the memory sockets.
When upgrading, be careful not to damage the SIMM sockets, especially if you are removing memory. Although the IIfx shipped with 4 MB of memory, odds are pretty good it's already been upgraded beyond that point.
Looking at the motherboard with the connectors to the rear and power supply to the right, you will see eight SIMM sockets. The four nearest the rear of the board are Bank A. The four nearest the front are Bank B. Memory must be installed in sets of four 64-pin SIMMs rated at 80ns or faster.
A 4 MB configuration has four 1 MB SIMMs in Bank A; an 8 MB configuration has 1 MB SIMMs in all eight sockets.
For 16 MB, install four 4 MB SIMMs in Bank A. To reach 20 MB, add four 1 MB SIMMs in Bank B.
For 32 MB, insert 4 MB SIMMs in all eight sockets.
Although the IIfx supports 16 MB SIMMs, Apple's memory guide gives no details on installing them. I suggest you install the first bank of 16 MB SIMMs in Bank A, since that follows the pattern established with other configurations. Bank B can then hold 1 MB, 4 MB, or 16 MB SIMMs.
After installing memory and reconnecting your drives, boot your Mac with extensions off (hold down the shift key) and check "About This Macintosh" under the Apple menu. If it doesn't give the expected number, you should reseat your memory.
Once you know the upgrade is a success, bolt everything back in place, attach the cover, and enjoy the extra memory. I suggest you increase the size of the disk cache for better performance.
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