OVM and UVM concepts - Highlights & Differences

Highlights:

• Constrained random, coverage-driven verification.
• configurable, flexible, test benches.
• Vertical and Horizontal re-use.
• Separation of tests/simulation from the test bench.
• Transaction-level communication (TLM).
• Layered sequential stimulus.
• Standardized messaging (turn-on and off the messaging of the component). 
• Register layer (Newly added in UVM)
• Enables programming and verifying registers (reg implemented in a design) in a consistent and efficient manner.

Differences:

• UVM is based on OVM 2.1.1
• The deprecated features from OVM were removed in UVM (deprecated.txt in the OVM install area).
• The URM and AVM compatibility layers were removed from UVM.
• Updates in UVM:
• Enhancements to the OVM callback facility, including a new message catching facility.
• Enhancements to the OVM objection mechanism.
• These enhancements introduce some minor backward incompatibilities to the OVM callback facility (UVM is nearly compatible with OVM).
• Other than this, it is a blind change from ovm_* to uvm_* for the whole library.
• UVM continues to evolve - 1.1 to 1.2.