According to BSN, the HD 7970 GPU will be made up from 32 Compute Units for a total of 2048 cores that operate at a 1GHz clock.
These will be linked via a 384-bit wide memory bus to 3GB of GDDR5 VRAM working in a quad data-rate mode at 1.37GHz (5.5GHz effective) in order to provide a whopping 264GB/s of memory bandwidth.
1) Truly functional Virtual Memory coming to GPU with AMD Radeon HD 7900 Series
2) AMD Compute Unit: Completely redesigned compute core features dedicated L1 and L2 memory, as well as shared L1 for MIMD functionality
3) With Tahiti packing 32 Compute Units in a maximum configuration, a 32 CU GPU with 2048 processing cores features almost 5MB of on-die memory: 512KB L1 Data cache, 384KB Shared L1 cache and 2MB of LDS and 2MB of L2 Cache. This is a record amount of cache for the GPUs so far, and you can expect this trend to continue.
The new GCN architecture brings numerous innovations to GPU architecture, out of which we see x86 virtual memory as perhaps one of the most important ones. While the GPU manufacturers have promised functional virtual memory for ages, this is the first time we're seeing a working implementation. This is not a marketing gimmick, IOMMU is a fully functional GPU feature, supporting page faults, over allocating and even accepting 64-bit x86 memory pointers for 100% compatibility with 64-bit CPUs. Virtual memory is going to be the large part of next-gen Fusion APUs (2013) and FireStream GPGPU cards (2012), and we can only commend the effort made in making this possible.