| Jo21 said: PPE only sync, but SPU can be working on background preparing to process data or helping the SPU. SPU have less cache, than PPE thats the main difference other being require DMA calls to move data. |
Not quite. The SPUs do not have a cache, they depend on their local memory that has to hold the programming code and the Data and only the Programmer is responsible for the management of this memory. The important thing of these units is that they can simultaniously send their old results and receive new data (via their own Memory Flow Controller) and calculate the current data. In theory all units could work continously but in such a situation 3 SPE (SPU+MFC) could block the bus (if they do not form a chain). Additionaly the PPE can execute two orders at the same time, the SPUs can only execute one order, but every SPU has an AltiVec 128 Engine but only one of the execution pipelines of the PPE has such a unit. There is one of the biggest differences to the Xenon which has two AltiVec 128 Units for each core (one per pipe).
