The 28 nm product line is divided in three dies (
Tahiti,
Pitcairn, and
Cape Verde), each one highly increasing shader units (32, 20 and 10 respectively). While this gives a high increase in single-precision floating point, there is however a significant departure in double-precision compute power.
Tahiti has a maximum ¼ double precision throughput relative to its single precision throughput, while the other two smaller consumer dies can only achieve a 1/16 ratio. While each bigger die has two additional memory controllers widening its bus by 128 bits,
Pitcairn however has the same front-end dual tesselator units as
Tahiti giving it similar performance to its larger brethren in DX11
tessellation benchmarks. The Radeon HD 7970 features 2048 usable stream cores, whereas the Radeon HD 7950 has 1792 usable stream cores, as 256 out of the 2048 cores are disabled during
product binning which detects defective areas of a chip. The cards are the first products to take advantage of
AMD's new "Graphics Core Next" compute architecture. Both cards are equipped with 3 GB GDDR5 memory and manufactured on TSMC's 28 nm process. The
Tahiti GPU is also used in the Radeon HD 7870 XT, released November 19, 2012. In this case one quarter of the stream processors are disabled, giving 1536 usable cores. Additionally, the memory interface is downgraded from 384-bit to 256-bit, along with a memory size reduction from 3 GB to 2 GB.
Radeon HD 7800 Codenamed
Pitcairn, the Radeon HD 7800 series was formally unveiled on March 5, 2012, with retail availability from March 19, 2012. Products include the Radeon HD 7870 and Radeon HD 7850. The Radeon HD 7870 features 1280 usable stream cores, whereas the Radeon HD 7850 has 1024 usable stream cores. Both cards are equipped with 2GB GDDR5 memory (some 7850s offer 1GB) and manufactured on TSMC's 28 nm process.
Radeon HD 7700 Codenamed
Cape Verde, the Radeon HD 7700 series was released on February 15, 2012. Products include the Radeon HD 7770 GHz Edition and Radeon HD 7750. The Radeon HD 7770 GHz Edition features 640 stream cores based on the GCN architecture, whereas the Radeon HD 7750 has only 512 usable stream cores. Both cards are equipped with 1 GB GDDR5 memory and manufactured in 28 nm. On March 22, 2013, another card, Radeon HD 7790, was introduced in this series. This card is based on the Bonaire architecture, which features 896 stream cores using 2nd Generation
GCN technology, an incremental update. In May 2013, AMD launched the Radeon HD 7730, based on the Cape Verde LE graphics processor. It features a 128-bit memory bus, 384 stream cores, 8 ROPs, and a core clock speed of up to 800 MHz. The HD 7730 came with GDDR5 and DDR3 variants, running on memory clock speeds of 1125 MHz and 900 MHz, respectively. Load power usage was lowered by 14.5% (47W) compared to the Radeon HD 7750 (55W). == Chipset table ==