Which of the following statements is / are NOT CORRECCT about NUMA ? (A) LOAD…
2023
Which of the following statements is / are NOT CORRECCT about NUMA ?
(A) LOAD and STORE instructions are used to access remote memory.
(B) There is a single address space visible to all CPU.
(C) Access to local memory is slower than access to remote memory.
(D) When the access thime to remote memory is hidden, the system is called NC - NUMA.
(E) In CC - NUMA, Coherent caches are present.
Choose the correct answer from the options given below :
- A.
(A) and (C) Only
- B.
(B) and (D) Only
- C.
(A) and (E) Only
- D.
(C) and (D) Only
Attempted by 51 students.
Show answer & explanation
Correct answer: D
Answer: The statements that are NOT correct are 'Access to local memory is slower than access to remote memory.' and 'When the access time to remote memory is hidden, the system is called NC - NUMA.'.
Why the first statement is incorrect: In NUMA (Non-Uniform Memory Access) systems, accesses to memory that is local to a processor are typically faster than accesses to remote memory. Remote memory accesses traverse an interconnect and therefore incur higher latency and often lower bandwidth.
Why the second statement is incorrect: NC-NUMA refers to non-cache-coherent NUMA (or non-coherent NUMA), meaning there is no hardware-enforced cache coherence across nodes. It does not mean that remote access time is hidden; hiding remote access latency is a different design goal/technique and is not the definition of NC-NUMA.
Quick review of the other statements:
LOAD and STORE instructions are used to access remote memory: True — from a programming perspective remote memory accesses use the same load/store operations, though they have higher latency.
There is a single address space visible to all CPUs: True for typical shared-memory NUMA systems — all processors can address a single global address space.
In CC-NUMA, coherent caches are present: True — CC-NUMA stands for cache-coherent NUMA, where hardware ensures cache coherence across nodes.