Effective Memory Clock, how important is it?

Amywalker730

Honorable
Nov 24, 2014
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I'm looking at the R9 295x2. One model, XFX Core, is selling for $630. The only difference, though please correct me if I'm wrong, is that it's listed effective memory clock is 5000MHz. This compares to the other models selling from anywhere from $750 to $1,000, all with 1250MHz (5.0Gbps).

What does this difference mean and is it significant enough to warrant an extra $120?