Useful expansions: SIMMchanger

I’m reprinting this brief review by Nigel Grey that appeared on the March 18, 1994 issue of MacUser UK because I think it’s useful for Mac vintage enthusiasts who may want to look for this item in the second-hand market (since I don’t believe you can still purchase it from MicroMac Technology).

As usual, I’m publishing this content in good faith and because I think it may be valuable information for my target audience. If the copyright owner has problems with this and requires the removal of the following material, I shall comply.

A converter board that lets you plug old 30-pin RAM SIMMs into a 72-pin socket.


Macs from the LCIII onwards use a new type of RAM SIMM with 72 pins. Older 30-pin SIMMs can’t be used, so if you upgraded your Mac with a logic board swap, the RAM SIMMs are redundant — unless you have something like SIMMchanger, a converter board that allows you to plug in up to four 30-pin SIMMs into a single 72-pin SIMM socket.

SIMMchanger can use 512KB, 1MB, 2MB or 4MB SIMMs. Two types of board are available — one with angled SIMM sockets for the LCIII and the other with straight sockets for the Quadra (Centris) 610, 650 and the 660AV. All these machines use 80ns SIMMs or faster, so older 120ns SIMMs used in the Mac II will not work properly.

We fitted SIMMchanger to a Centris 650 using four 30-pin 1MB SIMMs which should increase the total memory from 12MB to 15MB. Jumper switches needed to be set according to the SIMMs fitted to SIMMchanger, and, usefully, the configuration table is printed on the board. The Centris 650 has four SIMM sockets and SIMMchanger can go in any one but, if you want to fit SIMMs in the other slots, then it must go in the far left socket, looking from the front of the machine because of the width of the populated SIMMchanger board. The Mac has to be 32-bit clean to use SIMMchanger and if you want to access more than 8MB of RAM, the option must be turned on in the Memory control panel.

The Centris 650 rebooted without a hitch, and four 30-pin 80ns SIMMs culled from a Mac IIcx successfully boosted the Centris’ RAM to 15MB.

2 thoughts on “Useful expansions: SIMMchanger

  1. Cameron — Thanks for pointing that out. We regret the error and have corrected the article. The error, of course, was in the original article, and got me confused as well.


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