No, not at all. The difference at times is huge. 20-30%, or even higher in the right situations. This of course depends on the software and hardware being used, but additional ram bandwidth is often handy.
My core2duo@3.86ghz amithlon box loses about %25 in terms of framerates using software rendered Quake2. Using software rendered Wazp3d is significantly bigger an hit.
There's a reason triple and quad channel ram was introduced over the last few years, even with the advent of 2ghz+ ddr3 ram
