If running host-based sampler (like Soft SampleCell, or Unity) with 256...

If running host-based sampler (like Soft SampleCell, or Unity) with 256 MB of samples loaded, I assume that 256 meg of system ram must be free, yes?

Correct - 256 MB of system RAM for samples (assuming the soft sampler is using system RAM, like SSC) This, however, does not affect how much RAM is needed by Pro Tools. Pro Tools does not need extra RAM to run a host-based sampler using DirectConnect.

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