Just as word reaches us that JEDEC, the memory standards-setting organisation, has approved the Fully Buffered DIMM server memory system, RAM specialist Crucial UK said it had begun offering FB-DIMMs. We can see why: this stuff costs more than a top-of-the-range Itanic 2 processor.

A case in point is Crucial's 667MHz 4GB FB-DIMM, for which it wants a cool £4,023.19, sales tax included. Drop down to 533MHz and you only pay £3,291.16 inc. VAT.

In other words, the 4GB DIMMs cost more any Itanium 2 CPU. Intel's most expensive chip now comes in at $4,227, thanks to recent price cuts - that's £2,274 in English money.

Not that's Crucial doesn't offer good value for money: you can buy a 512MB 533MHz FB-DIMM for just £77.54 inc. VAT, more expensive than only a handful of low-end Celeron D processors. A gigabyte FB-DIMM will currently set you back a mere £137.46 inc. VAT.

It's not really Crucial's fault that FB-DIMMs are so pricey. The going rate is a sign of their relative scarcity - memory makers only began sampling the stuff last year - and the very low level of demand. Now that JEDEC's given the serial interface memory system the thumbs-up, prices should fall. Wider availability of motherboards capable of using the memory system - it's a key feature of Intel's Xeon DP-oriented 'Bensley' platform, for example - will help too. We expect all other memory makers to be charging pretty much what Crucial is.

AMD isn't expected to engineer is Opteron server processors to support FB-DIMM until 2008, the same timeframe Intel is expected to ship Itanium CPUs with a built-in FB-DIMM memory controller.

FB-DIMMs use a new two-way, point-to-point bus. All instructions sent to a given FB-DIMM's memory chips to read or write data are stored and then forwarded by each DIMM ahead of it in the chain. The memory addresses and the clock timings are buffered too. Data is sent back and forth in packets, co-ordinated by the DIMMs' Advanced Memory Buffer (AMB) chips, to eliminate errors and signal interference. ®