COMPUTER SCIENCE TRIPOS Part II – 2021 – Paper 8
Comparative Architectures (rdm34)
(a) Some VLIW processors exploit fine-grain multithreading and SIMD execution
units.
(i) What benefits could adding support for fine-grain multithreading to a
VLIW processor provide? [4 marks]
(ii) Why might a simple round-robin thread schedule be inefficient and how
could we improve the schedule? [2 marks]
(iii) Assuming the VLIW processor has taken full advantage of fine-grain
multithreading with a simple round-robin thread schedule, what changes
to the processor might an optimised thread schedule require to ensure
programs continue to execute correctly? [4 marks]
(iv) Why might it be useful to include SIMD functional units when a VLIW
processor can already specify independent operations to be executed in
parallel? [4 marks]
(b) Some VLIW processors support variable-length bundles of independent instructions.
(i) Why is this a useful feature and how could it be supported? [2 marks]
(ii) What costs would be incurred and additional logic needed to support this
feature? [4 marks]