G3MX: more DDR3 for Opterons

AMD just revealed G3MX (Socket G3 Memory Extender) technology which allows a significant extension of memory on platforms based on Opteron processors. It will enable the continual use of DDR3 in DIMM format rather than relying on costly FM-DIMM as Intel does with some Xeons amongst others.

Developed in coordination with IDT and Inphi, in practice it translates to an added buffer on the motherboard which controls memory modules. This has the advantage of being more economical than installing a buffer on each module, as is the case with FB-DIMM. Each processor should then be able to support up to 16 memory modules via G3MX. The impact on latencies should also be less than with the rival technology. Finally, as AMD has integrated memory controllers on its CPUs, there is the added advantage of not having to modify them to increase the amount of memory.

Expected out in 2009, AMD told us in May at the CTO Technology Summit that the G3MX technology would be implemented to future Opteron quad and octocores based on the Montreal architecture. This architecture will be the last evolution of the K8 core before an entirely new one, but will be the first to use G3MX. This will be optional because it will still be able to use memory in a more classic way.