AMD will launch its first graphics card in the Radeon HD 7000 family during the fall and as expected it will be the first VLIW4 circuits at 28nm. The top models of the Radeon HD 7900 series aims higher and will according to recently leaked roadmaps use the AMD Graphics Core Next architecture and the high speed memory XDR2 from Rambus.
Radeon HD 7000 will like the current 6000 family launch in steps and with different base architectures. If we are to believe the latest information that is said to come from AMD’s leaked roadmap the graphics card marker is aiming for a first launch in Q4 2011. Then it will be the latest VLIW4 architecture (Very Long Instruction Word) that is on the menu and it will most likely have the same base as the Radeon HD 6900 series. An archtiecture that will be more efficient than VLIW5 that was used by other Radeon HD 6000 cards.
AMD’s first 28nm circuits may be based on the same base as Radeon HD 6900 series
AMD is planning four different GPUs based on the 28nm version of the VLIW4 architecture and use them in three different series, Radeon HD 7800, HD 7600 and HD 7500. The four GPUs will be equipped with 768 to 1536 Radeon cores (stream processors) and GDDR5 memory in high speeds.
| 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 |
Radeon HD 7870 is the top model based on the GPU Thames XT and according to the documents they will be made with TSMC’s 28 nanometer HPL technology (High Performance Low-power). Despite specifications that are similar to the current top model Radeon HD 6970 – actually higher on several points – Radeon HD 7870 will get a maximal power consumption of only 120 watt, which is more than half of the 250 watt the 40nm precursor consumed.
Besides Thames XT we also have Thames Pro, Lombok XT and Lombok Pro where all use the same efficient 28nm technology with power consumption down to 50 watt.
Radeon HD 7900 series looks to be a question for the future – just like the Radeon HD 6900 series was. The reason is quite simple and it is abbreviated GCN. AMD Graphics Core Next is whole new and from the ground up designed GPU architecture that AMD has been talking about for some time now. The company has used a more programming friendly approach that will improve performance and functionality in GPGPU applications.
We have no concrete information on when Radeon HD 7900 series will launch, but most likely Q1 2012. AMD has chosen to use a more performance oriented node, TSMC’s 28nm HP (High Performance) that will be ready later than HPL, but also have switched from GDDR5 to the pretty untested XDR2 technology.
XDR2 is made by Rambus and is marketed as the world’s fastest memory system. Rambus claims that XDR2 offers twice the bandwidth of GDDR5 per circuit, while power consumption will be 30% less at the same performance.
The information that has leaked on Radeon HD 7900 series says that AMD will pair the new architecture with XDR2 memory at up to 8000 MHz, which in the flagship would result in a memory bandwidth of 256 GB/s over a 256-bit memory interface, comparable to 176 GB/s in Radeon HD 6790 with GDDR5 memory at 5500 MHz.
| 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 |
The unconfirmed information says that the flagship Radeon HD 7970 (Tahiti XT) will ship with 2048 Radeon cores and a GPU frequency of 1000 MHz, which should result in a performance to remember, but despite that the power consumption will only be 190 watt, thanks to the new node technology.
Radeon HD 7950 (Tahiti Pro) and Radeon HD 7990 (New Zeeland) are also mentioned. Where the latter is the first graphics card with dual GPUs based on the Graphics Core Next architecture.
AMD looks to have something really exciting coing over the coming six months, but this is unconfirmed information that we may very well be fake. Either way it sounds likely that AMD will start its 28nm launch of Southern Islands with VLIW4 and later introduce Graphics Core Next. Whether the untested XDR2 memory technology will appear or not, we don’t know, but if so it will be worth to look closer at.
Source: Expreview.com
