Intel Corp. said it would not support fully-buffered DIMMs in its desktop platforms because of high costs of FB-DIMMs amid necessity of personal computers to be very affordable. The move is likely to alter the memory market and even have an impact on Intel’s arch-rival Advanced Micro Devices.

“Currently we have no plans to support FB-DIMM technology on desktop platforms because these platforms target the volume market. Naturally, this market can’t accept too much additional cost. This is the main reason why we will continue to support standard unbuffered DIMMs,” said Sunil Kumar, Intel’s director of chipset marketing, in an interview with DigiTimes web-site.

FB-DIMMs utilizes JEDEC-standard DDR2 SDRAM chips, but the modules’ design is completely new: in the FB-DIMM, all signals – clock, address, command and data – to and from the DRAM on the module are buffered at the high-speed Advanced Memory Buffer (AMB) chip located on the DIMM. This helps to secure the DRAM timing margins during high-speed operation with a much shorter signal path between the DRAM and the AMB.

The FB-DIMM also adopts a Point-to-Point serial connection on the bus between the memory controller and the DIMM, as well as between the DIMMs themselves. This allows increased bus speed with a shorter connection path. It also greatly improves the maximum number of DIMMs that can be loaded on the bus – up to eight 2-rank DIMMs – with less concern about signal degradation. Current DDR2 platforms face issues with density scalability (only 8 – 12GB of memory can be installed per single memory controller), which is why Intel does not introduce DDR2 support for the Intel Itanium 2 platforms that are intended for high-end servers with 16GB or even more memory.

In case the usage of FB-DIMM will be limited to Intel-based servers, then the industry will have at least two different memory types and infrastructures for different applications. While this is not a problem for Intel Corp., who supplies different logic for servers and desktop, its rival Advanced Micro Devices, whose processors have integrated memory controller and support of only one memory type across the board, will have to either differentiate its servers and desktop chips, or can the support of FB-DIMM.

AMD has not yet introduced its processors with support for DDR2 memory and even has not provided any likely timeframe of the move other than saying “when DDR2 makes sense” in terms of price and performance. Since desktop platforms do not require high memory densities, the DDR2 will plug into AMD-based PCs absolutely fine, but in the server space AMD may face DDR2 density scalability problems. Currently AMD64 processors for desktops, workstations and servers with built-in memory controller support DDR memory. When the DDR2 era comes for AMD, it will have to choose whether to implement FB-DIMM support into server-oriented chips or stick to DDR2 or even DDR1.

It is unclear whether FB-DIMMs will be available widely, provided that they will only be supported by server infrastructure of Intel Corp.

The first FB-DIMM server platform is expected to emerge in 2006.