Bridges connected to each other through FSB

Posted Sep 26, 2007 18:20 UTC (Wed) by csnook (guest, #36935)
In reply to: Bridges connected to each other through FSB by giraffedata
Parent article: What every programmer should know about memory, Part 1

The northbridge is the barrier between the CPU domain (FSB, HT, etc.), which has to deal with cache coherency, locking, interrupt delivery, etc. and the rest of the system, which simply passes serial messages or parallel data/address tuples around. On a sufficiently primitive system you don't really need one, but all modern commodity microarchitectures have something like a northbridge either on the chipset or the processor itself.

As for bottlenecks, even if the northbridge itself has enough internal bandwidth between all of its ports to function in a non-blocking fashion, you can't have a bottleneck-free network unless both the CPU and the I/O controllers have dedicated bandwidth to the memory. That only makes sense with multi-port DRAM, which isn't used for main memory in any commodity system.