Using several texture units, or fetching several times

Hi there

I have a texture, into which i want to lookup several times (just like when doing a box-filter or something).

Now, would it be faster to bind that texture to more than one unit and to lookup into each unit only once, or would it be faster to do several lookups into one unit.

The thing is, that i lookup a texel and its neighbouring texels, so i will almost always hit the texture-cache.

And what if i do several lookups into the same texture, but not at neighbouring texels? Does every texture unit have its own cache, so that it then will be faster to utilize several units?