Hardware news: XDR - Bandwidth
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This is where XDR will shine. Currently, the most extreme overclockers combining the top of the line computer parts can push the memory bandwidth to 9.0 GB/sec. Most people won’t be seeing this kind of performance until the end of DDR2 or later. XDR will start at 9.6GB/sec, and the current highest is 16GB/sec with higher on the horizon.
The biggest complaint made about DDR2 is their latency. Latency plays a role in the overall bandwidth. DDR has a latency of roughly 10 ns, while DDR2’s latency is closer to 15ns. This is why DDR beats DDR2 at the same speed. XDR's latency will be lower than that of DDR. It will be available in latencies of 1.25/3.0/2.5/3.33 ns. This will provide an additional advantage over DDR2. The clocks should remain on par with DDR2, but when XDR is clocked to higher speeds the gap will grow further.
FlexIO
Rambus has created a new technology called FlexIO, it is made up of two parts, FlexPhase and DRSL.
FlexPhase will allow precise on-chip alignment of data with clock. This doesn’t mean as much to consumers as it does motherboard manufactures. The manufactures don’t need to be worried about PCB trace lengths matching and PCB timing constraints. Even wonder why when you look at motherboards the traces seems to run in funny patterns? This is because current memory technologies need the entire tracer lengths from the memory to the memory controller needs to be the same length. If all the tracers are the same length, then every bit of info will arrive in the right order. If the tracers are different lengths, data with the shorter route will get there faster then data from a longer tracers. For consumers this means that motherboards can be a lot simpler, thus smaller, and maybe cheaper.
Differential Rambus Signaling Levels (DRSL) is the other part of FlexIO. The whole idea of computer advancement is to get the parts faster and cooler. The quickest way of cooling it down is decreasing the voltage. With this in mind we will look at what DRSL does. Normally the lower the voltage becomes the harder it is to distinguish between the electrical “high” and “low”; it is easier for the computer to tell the difference between 3.0 volts and 0 volts then .09 volts and 0 volts. DRSL will use the difference between two voltage lines with a little voltage difference and use that difference for its signaling. This means the overall memory voltage and be decreased to about 1.8 volts.
Playstation 3
As I mentioned above, the Playstation 3 will pack a whopping bandwidth with XDR. While a lot is not known about the Playstation 3, reports have been that the unit will sport XDR, making it the first in-demand product using XDR. The specifications for the amount and speed of memory are still unknown, but rumors are of between 25.6 GB/sec to as high as 51.2 GB/sec. In contrast, the Playstation 2 supports a theoretical limit of 3.2 GB/sec.
Nvidia will be providing the graphics processor for the unit, so you will likely see the next generation of Nvidia graphics cards using XDR also. It is cheaper for Nvidia to carry over the XDR than try to create a new card with different memory. In case anyone is wondering, the CPU being used is called “cell” and can be clocked up to 4 GHz. Better graphics and bigger battles are on the horizon for the gamers out there.
Next: The Cell >>
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