AMD Radeon HD 7870 and 7850 GPU Previews

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Radeon HD 7870 and 7850

The card you see pictured directly below is the Radeon HD 7870 GHz Edition. The Radeon HD 7870 is outfitted with a fully functional Pitcairn GPU with all of its CUs and texture units intact and enabled.


AMD Radeon HD 7870 GHz Edition

As the full name of this card suggests, the Radeon HD 7870 GHz Edition’s GPU is clocked at a cool 1GHz—a second for a reference GPU from AMD (the Radeon HD 7770 was the first). With a 1GHz Pitcairn GPU paired to 2GB of GDDR5 memory clocked at 1.20GHz (4.8Gbps data rate), the Radeon HD 7870 offers up 2.56 TFLOPS of compute performance, with a texture fillrate of 80GT/s, a pixel fillrate of 32 GP/s, and peak memory bandwidth of 153.6 GB/s.

The Radeon HD 7870 GHz Edition card is outfitted with a dual-slot cooler, but has a relatively modest (in light of higher-end cards) 9.5” PCB. With a 175W TDP, the Radeon HD 7870 requires a pair of 6-pin PCI Express power feeds, and its outputs consist of a single HDMI output, two mini-DisplayPort 1.2 outputs, and one Dual-Link DVI output.


AMD Radeon HD 7850

The Radeon HD 7850 has the same output configuration as the Radeon HD 7870, but its Pitcairn GPU is pared down somewhat. The GPU at the heart of the Radeon HD 7850 has four of its compute units disabled, so “only” 1,024 stream processors and 64 texture units are enabled. The GPU is also clocked lower at 860MHz. The Radeon HD 7850’s differences result in 1.76 TFLOPS of compute performance, with peak texture and pixel fillrates of 55 GT/s and 27.52 GP/s, respectively. The card’s memory, however, is clocked at the same 1.2GHz as the Radeon HD 7870, so memory bandwidth remains unchanged at 153.6 GB/s.

With its pared-down, lower clocked, GPU, the Radeon HD 7850 requires less power than the Radeon HD 7870—130w vs. 175w. As such, the Radeon HD 7850 can get by with only one additional 6-pin power feed (75w is supplied by the slot, 75w by the additional 6-pin feed). The reference Radeon HD 7850 we received for testing has the same 9.5” PCB and dual-slot cooler design as the 7870, but some non-reference cards due to hit retail shelves will sport shorter, 8.25" PCBs.

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