More Cogs from One Prop

Humanoido

Is it possible to create one or more extra tiny virtual cogs inside a Prop chip?

Humanoido

Leon

You could create threads running on a cog.

Humanoido

Leon wrote: »

You could create threads running on a cog.

Leon, ok let's create one extra thread, with a drop-in path for more. Can one of the Forum prop software experts show how to get started and maybe create some simple example using SPIN?

Humanoido

Leon

I'm fairly sure that someone has already done it.

Heater.

Humanoido,

Have a look at FullDuplexSerial. Note the cunning way it has two threads of execution going on. One for transmit and one for receive. That technique is generally referred to as coroutines (as opposed to subroutines). One returns to the other which returns to the first and so on.

Perhaps not quite inside a COG but you might think about making and LMM execution loop that has multiple LMM Program Counters and hence executes two or more threads of LMM code sort of at the same time.

So four threads might look like so:

LMM_loop    rdlong LMM_1, PC_1
            add    PC_1, #4
LMM_1       nop
            rdlong LMM_2, PC_2
            add    PC_2, #4
LMM_2       nop
            rdlong LMM_3, PC_3
            add    PC_3, #4
LMM_3       nop
            rdlong LMM_4, PC_4
            add    PC_4, #4
LMM_4       nop
            jmp    #LMM_loop

Edit: Not sure it's possible to make a thread example in Spin. Someone here did recently post some ideas and code for implementing threads in COGs. Can't remember who...

Edit: I hate those stupid code boxes with totally unnecessary scroll bars.

John Abshier

There is a Prop RTOS pointed to by the 2009/2010 Propeller Design Contest sticky thread.

John Abshier

Humanoido

Peter (pjv) - Prop RTOS " Depending on complexity and speed, a Cog can have any number of independent threads. Contrived applications such as simple LED flashers can have 128, but more intensive, practical, programs more likely 8 to 16 threads per Cog."

Thanks Leon, Heater, John Abshier (and PJV). 8 to 16 threads per Cog, up to 128 for LEDs - This is fantastic! It puts this project in a new perspective. With a 320 Cog machine, tiny processor threads could yield totals ranging from 2,560 processors to 40,960 processors.

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