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This item is from the PC Hardware FAQ, by Willie Lim and Ralph Valentino with numerous contributions by others. (v1.25).

2.18 Will 9 chip and 3 chip SIMMs work together?

[From: cls@truffula.sj.ca.us (Cameron L. Spitzer)]

Almost always. But there are exceptions.

1. Some motherboards do not supply enough refresh address bits for a 4Mb x1 or a 1Mb x4 DRAM. These old motherboards will not work with 4 MB 9-chip SIMMs or 1 MB 3-chip SIMMS.

2. Some EL CHEAPO motherboards do not have proper terminations on the lines which drive the DRAM array. These boards may show only marginal compatibility with various SIMMs, not working with all prefectly good SIMMs you try, favoring SIMMs with parameters skewed towards one end or another of the allowed ranges. In some cases, most of the SIMMs you happen to try might be 9-chip modules, and in other cases they might be 3-chip modules. A random selection of a dozen SIMMs might lead you to conclude the motherboard doesn't "work" with 3-chip modules, or with a "mixture" of 3-chip and 9-chip modules.

You might find the real solution is to use SIMMs one speed faster than the manual calls for, because the particular motherboard design just cuts too many things too close.

 

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• prev: 2.17 What speed SIMMs do I need?
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• next: 2.19 What are "single-sided" and "double-sided" 72-pin SIMMs?

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