The key difference between interleaved multi-threading and simultaneous multi-threading is that every clock, core chooses instructions from one / multiple threads to run. (Slide 57)
Multicore processor: Multiple processing units on one processor
SIMD Execution: "Single instruction multiple data". One instruction decoded, and sent to all ALUs, which perform that instruction on different data.
Coherent control flow: Same instruction performed on each element and needed for SIMD execution
Hardware multithreading: the hardware (processor) figures out which threads should run when.
Interleaved multithreading: one thread is chosen to run at any given clock
Simultaneous multithreading: instructions that can run at that time are run on ALUs at each clock.
Memory latency: time it takes for processor to request data and receive it.
Memory bandwidth: a rate of how much data can go to the processor and back during a certain amount of time.
Bandwidth bound application: bottleneck due to requesting and receiving things from memory.
Arithmetic intensity: ratio of math to data access operations
"explicit SIMD" --> parallelization preformed @ compile time (CPUs)
"Implicit SIMD" --> compiler creates scalar instructions... hardware does parallelization (GPUs)
coherent control flow is the same thing as coherent execution, correct?
@MaxFlowMinCut: yes, you are correct. Coherent control flow on this side is the same concept as coherent execution on slide 36.
@kayvonf So when we talk about hardware multithreading, with multiple contexts, this entails both IMT and SMT: at each clock, (lets say there are 2 F/D units) the processor can choose 2 instructions from the pool of instructions available from the 2 or more hardware threads. If there are say 4 hw threads, then we can have a following execution sequence:
i: 1 & 1
i+1: 1 & 3
i+2: 2 & 4
i+3: 2 & 2
There isn't a notion of context switching at this level right? The processor can access all contexts at the same time?
So then is SMT a capability of the processor? It either supports it or doesn't.