AMD Radeon HD 7900 to Utilize New XDR2 Rambus Memory

AMD is set to launch its next-generation graphic processors this coming fall and it is shaping up to be more than expected with use of XDR2 memory interface.


Based on a leaked road-map, AMD will be releasing their new GPUs in Q4 for the upcoming holiday season. The GPUs will start with four different GPUs based on the 28nm version of the VLIW4 (Very Long Instruction Word) architecture. The four GPUs will be equipped with 768 to 1536 Radeon cores (stream processors) and GDDR5 memory.
Graphics card Radeon HD 7870 Radeon HD 7850 Radeon HD 7670 Radeon HD 7570
Node TSMC 28nm HPL TSMC 28nm HPL TSMC 28nm HPL TSMC 28nm HPL
Architecture VLIW4 VLIW4 VLIW4 VLIW4
GPU Thames XT Thames Pro Lombok XT Lombok Pro
Radeon cluster 24 22 12 12
Radeon cores 1536 1408 768 768
GPU frequency 950 MHz 850 MHz 900 MHz 750 MHz
Texture units
96 88 48 48
ROPs 32 32 16 16
Graphics memory
2GB GDDR5 2GB GDDR5 1GB GDDR5 1GB GDDR5
Memory frequency
5800 MHz 5200 MHz 5000 MHz 4000 MHz
Memory interface
256 bit 256 bit 128 bit 128 bit
Memory bandwidth
186 GB/s 166 GB/s 80 GB/s 64 GB/s
Power consumption
120 watt 90 watt 60 watt 50 watt

The fun begins when you start to look at the new high-end GPUs codenamed "Tahiti", which is expected to see a Q1 2012 release. The "Tahiti" will make use of PCIe Gen3 interface, which has a massive bandwidth of 32 GB/s. The 7900 series is set to utilizes new AMD's Graphics CoreNext GPU architecture. The GCN is expected to boost performance per square millimeter die area to improve upon the VLIW4 architecture .

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The most interesting change is AMD's decision to go with XDR2 memory interface from Rambus over previous generation DDR5 memory interface. Rambus claims the XDR2 is twice as fast as DDR5, while offering 30 percent less power consumption.

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Read more about Rambus' claim.

Additional information leaked has the Radeon HD 7970 series with, 2048 Radeon Cores, GPU frequency of 1000 MHz and XDR2 memory at 8000 MHz, which would result in a memory bandwidth of 256 GB/s over a 256-bit memory interface. This compared to the 176 GB/s in Radeon HD 6790 with GDDR5 memory at 5500 MHz. All this power will be packed within an estimated power consumption of 190 watts
Graphics card Radeon HD 7970 Radeon HD 7950 Radeon HD 6970
Node TSMC 28nm HP TSMC 28nm HP TSMC 40nm
Architecture GCN GCN VLIW4
GPU Tahiti XT Tahiti Pro Cayman XT
Radeon cluster 32 30 24
Radeon cores 2048 1920 1536
GPU frequency
1000 MHz 900 MHz 880 MHz
Texture units
128 120 96
ROPs 64 64 32
Graphics memory
2GB XDR2 2GB XDR2 2GB GDDR5
Memory frequency
8000 MHz 7200 MHz 5500 MHz
Memory interface
256 bit 256 bit 256 bit
Memory bandwidth
256 GB/s 230 GB/s 176 GB/s
Power consumption
190 watt 150 watt 250 watt

There looks to be some interesting times ahead for AMD in the coming months for us to keep watch. AMD will be releasing its new "Bulldozer" architecture, along with the new GCN architecture for the 7900 series GPUs (if the information leaked is accurate).
source : http://www.tomshardware.com/news/amd-HD-7900-XDR2-Rambus-Memory,13408.html