Rambus unveils 8GHz XDR 2

Five times faster than GDDR claim

By Tony Smith • Get more from this author

Posted in PC Builder, 7th July 2005 12:02 GMT

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Rambus has announced the second generation of its XDR high-speed memory technology, which the company claims will run five times faster than today's GDDR graphics memory.

Dubbed XDR 2, the technology will provide initial clock speeds of 8GHz. XDR 1 operates at up to 6.4GHz.

The new version of XDR incorporates four key technique, three of which are geared toward eliminating unwanted side-effects within the memory sub-system circuitry that hinder signals.

Rambus said it has tweaked XDR's FlexPhase timing circuits to adapt timing to compensate for "process, voltage and temperature variations during real-time operation". A separate output circuit likewise compensates for "adverse system effects" such as signal attenuation and reflected signals - the latter are further reduced by the architecture's terminated point-to-point topology. XDR 2 also uses a 200mV differential signalling system to suppress noise.

In addition, XDR 2 incorporates micro-threading, a patent-pending technique Rambus introduced last April, when it began licensing the concept. Micro-threading can be added to DRAM chips for a "relatively low incremental cost", the company said at the time, without going into details.

The technique involves partitioning the memory chip's storage into separate addressable areas, to which data requests can be sent in parallel, allowing the memory controller to send, say, four data requests in the time it would previously have taken it to send just one.

Rambus is pitching XDR 2 at graphics applications as the successor to today's GDDR chips. Rambus claims ownership of key components of GDDR and is currently suing five memory makers which it alleges have infringed its intellectual property rights.

The new version of XDR is available for licensing immediately, the company said, but it won't be until 2007 at the earliest before XDR 2 appears in shipping product.

XDR 1 has already been adopted by Sony for incorporation into the PlayStation 3. Samsung began shipping 256Mb XDR DRAM chips earlier this year. Memory maker Elpida has also licensed XDR. ®