LTAG Branch Predictor

[david-kooi]

A couple questions:

What is RAS? I try running TAGE by itself and I get a pre-fetcher issue:

This is fixed by making the 1st branch predictor 2bit.
Does 2bit always have to be included?

Then, what is the benefit of running multiple branch predictors?
From the point of view of the simulation are they executed in parallel?

Thanks

--
+1 Curiosity:
Running the TAGE branch predictor uses a lot of memory compared to 2bit and 2level. It crashes on my laptop with 16GB memory because memory consumption keeps increasing. Why is that?