Do all non-computable functions grow faster than computable functions?
In Does the Busy Beaver function grow faster than the Tree function?, the informal proof hinges on non-computable functions such as Busy Beaver growing faster than computable ones such as TREE. Is this necessarily given? For example, a trivially non-computable function which grows slower than TREE would be the sum of reciprocals of Busy Beaver: $$\sum_{i=1}^n\frac{1}{BB(n)}$$
Your example gives a counterexample to your question, if you allow real-valued functions. Another is $f$ defined by $f(n)=0$ if the $n$th Turing machine halts, else $f(n)=1$. The key thing about Busy Beaver isn't just that it's noncomputable, it's that it gives an upper bound on how long a terminating Turing machine can run, and thus on the size of any computable function. There are lots of other noncomputable functions out there that don't do this.
Let $f(x)=1$ if we can write $x=2^a3^b$ where $BB(a)=b$, and $f(x)=0$ otherwise. This $f$ is also noncomputable, and takes values only in $\{0,1\}$.
