Re: Is there a "reset" circuit in modern RAM chips?
I don't know of any large RAM chips that have memory reset hardware. The high speed, small size requirements mean that there can be no "extra" gates or wiring added.
Real RAM chips are not made of DFFs and multiplexors. The circuitry would be much too big.
The boot code accesses the RAM to determine its size and may do a quick memory test, but is not required to zero the RAM. The OS assumes that it is starting with uninitialized RAM. In general, you should assume that library calls like alloc() return uninitialized memory.