Re:BOOM Open Source RISC-V Core Runs on Amazon EC2 F1 Instances
by TomVDB on Thursday December 13, 2018 @11:01AM
(#18673272)
Less time spent waiting: yes.
Like reading from disk: no.
The max amount of out-of-order instructions is typically around 300 these days?
Reading from disk takes millions of cycles.
It’s about avoid waits when reading from L1 and L2 cache and DRAM.
Re:BOOM Open Source RISC-V Core Runs on Amazon EC2 F1 Instances
by zozbot123 on Thursday December 13, 2018 @11:52AM
(#18673767)
Yup, reading from disk will trigger a context switch from the OS, whether it happens explicitly or via a page fault involving virtual memory. (The closest parallel to that at the hardware level would be SMT.) As an aside, another rationale - perhaps a more paradigmatic one - for OOO involves achieving full use of super-scalar execution units on a processor core, when instructions have complex dependencies on one another.
The main advantage is higher IPC -> better performance since there is less idle time spent waiting for slow stuff like reading from disk.