ATI RV870, R800 information -- More transistors than GT200?

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German site ATI-Forum probably scored a coup of 2009 - according to
their sources, ATI's RV870-based cards are already out at selected
partners.

We cannot say was this leak was a reaction on our joint-exclusive
story about nVidia's GT300 architecture, but one thing is for sure -
ATI wants to bring out their Cypress board as soon as possible -
planned for July 2009.

The alleged specifications of RV870 reveal that this chip is not
exactly a new architecture, but rather a DirectX 11-specification
tweak of the RV770 GPU architecture. Just like nVidia's GT300
architecture, the actual RV870 chip is manufactured in TSMC's 40nm
half-node process, packing more transistors than GT200 chips.
Regardless of what ATI says about nVidia and large dies, the fact of
the matter is that ATI is making a large die as well - but the company
will continue to use the dual-GPU approach to reach high-end
performance.

The RV870 chip should feature 1200 cores, divided into 12 SIMD groups
with 100 cores each [20 "5D" units], while RV770 was based on 10 SIMD
group with 80 cores total [16 "5D" groups consisting out of one "fat"
and four simpler ones]. Thus, it is logical to conclude that when it
comes to execution cores, not much happened architecturally - ATI's
engineers increased the number of registers and other demanding
architectural tasks in order to comply with Shader Model 5.0 and
DirectX 11 Compute Shaders. The core is surrounded with 48 texture
memory units, meaning ATI is continuing to increase the ROP:Core:TMU.
For the first time, ATI is shipping a part with 32 ROP [Rasterizing
OPeration] units, meaning the chip is able to output 32 pixels in a
single clock.

When it comes to products, ATI plans to launch four parts: Radeon HD
5850 and 5850X2 in more affordable pricing bracket and HD5870 and
HD5870X2 for the high-end parts. While there were no clocks for the
Radeon HD 5850/5850X2 parts, alleged clocks for HD5870 and HD5870X2
reveal that for the first time, an X2 part is clocked higher than a
single-GPU part. Was this a requirement of SidePort memory interface,
we are not aware atm.
 

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