Friday, April 8, 2011

Miscommunication between AMD and its AIBs results in more ROPs enabled on the Radeon 6790 than intended

A possible miscommunication between AMD and its foundry or board partners saw some, if not all partners ship AMD Radeon HD 6790 graphics cards with more ROPs enabled than specified. The HD 6790 SKU is originally specified to have 16 of the 32 ROPs on the 40 nm Barts GPU enabled, however, batches of GPUs shipped have 24 out of 32 ROPs enabled. While not a bad thing for the user at all (since the GPU ends up with more geometry crunching power at its disposal), it has AMD red faced, as it disturbs the product lineup.

The issue surfaced when GPU-Z started reading ROP count of our samples as 24, even as AMD press deck and subsequently the product page on AMD website mentioned HD 6790 ROP count as 16. We initially dismissed it as a GPU-Z bug, but as it turns out, HD 6790 indeed has 24 ROPs enabled, if GPU-Z reads so. An ROP (raster operations processor) handles a key part of the GPU's geometry rendering. ROPs process final shader output pixels and put them into memory. 24 ROPs theoretically gives these few HD 6790 cards 50% higher geometry processing power. This isn't the first time AMD fumbled with specifications. Some of the first AMD Radeon HD 4830 graphics cards shipped with 80 stream processors less than specification; more recently, some initial Radeon HD 6850 samples had all 1120 stream processors of Barts enabled. They're supposed to have 960. AMD said that it is investigating into the matter, and could make an official statement soon.

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