Now I disable the reading of data by the first thread and check the speed of reading from system RAM.

Pic.28: Intel Conroe. Sequential reading of the data from system RAM.

Pic.29: Intel Conroe. Random reading of the data from the system RAM.

This processor works much more efficiently with system memory as you can see (Picture 28, 29). The higher speed of work with memory explains the lower latencies when reading modified data in another core’s L1 data cache in comparison with the Yonah.

So, the speed of data transfers between the cores is much higher in the Conroe than in the Yonah, but the modified data, if located in L1 data cache, are still transferred using the system bus.