REgarding thread fast mode

[lokesh327]

Hi,

I am working on xmos avb board for audio processing and I am using talker and listener seperately.

I have a question regarding thread_fast_mode, on my listener hardware, I have two tiles running 8 threads each. tile 0 runs for listener, media clock server and tile 1 runs the ethernet stuff and ptp.

I know that we have this thread_fast_mode_on function which makes a particular thread run faster compare to other threads.

I need information regarding this, whether this thread_fast_mode supports only one thread in both the tiles or each tile can run one thread in thread_fast_mode

Thanks in advance

[Ross]

Hi, the thread (or core rather) doesn't run any faster - it is just always scheduled in the pipeline.

From the XS1 Architecture Manual:

To enable the virtual processor to perform one input or output per virtual cycle, a fast- mode is provided. When a thread is in fast-mode, it is not de-scheduled when an instruction can not complete; instead the instruction is re-issued until it completes.

(Yes I realise "fast" mode is not a great name. Maybe think of it as "fast response" mode)

This mode does have a drawback in that it can reduce the MIPS available to other cores. Since the core in fast mode is always re-issuing it's paused instruction.

In reality the speed-up is very small - so I would not concern yourself with this mode unless you are very on the edge (like within a cycle or two) or you *really* know what you are doing.