After a PR disaster for AMD, the Radeon HD 4000 series is revealed a few days earlier than expected

If you’ve already read our story on Nvidia’s GeForce 9800 GTX+, then you’ll know that ATI’s ‘secret’ next GPU architecture is no longer a secret, as various sites, such as PC Perspective, have already decided to open their cans of confidential and spill both beans and worms everywhere. The result is that ATI has had to admit defeat, and has now decided that everyone can get a fair look at what the new Radeon HD 4000 GPUs have in store. So, without further ado, let’s get on with the show.

First off is the 55nm core of both the Radeon HD 4850 and 4870, codenamed RV770, which contains 965 million transistors. There have been various rumours about the spec of this chip, including talk of it having 480 stream processors. However, the truth is much more remarkable, as the chip actually has 800 stream processors, along with 40 texture units and 16 ROPs. The speed of the core is then down to the model of card, with the 4850’s core clocked at 625MHz, and the 4870’s core clocked at 750MHz.

Then we have the memory, with 512MB of 993MHz (1,986MHz effective) GDDR3 memory and a 256-bit memory interface on the 4850, and a bank of GDDR5 memory on the 4870, which has a total bandwidth of 3.6Gb/sec. The 4850 also has a single-slot cooler, and a single six-pin PCI-E power connector.

Some of the previous rumours had some truth in them, though, particularly when it comes to RV770’s new features. As revealed previously, the new GPU features 24x custom-filter anti-aliasing (CFAA), as well as AMD’s new marketing phrase: the TeraScale graphics engine, which promises high resolutions and fast frame rates.

As you would expect, the new GPU architecture supports DirectX 10.1, PCI-E 2.0 and CrossFire X, and it supports 7.1 audio via HDMI for copy-protected HD movie playback too. The GPU also features ATI’s Unified Video Decoder 2, which can decode both MPEG-2 and H.264 video streams, taking the work away from your CPU.

As well as various websites now offering the details of RV770, some graphics card manufacturers have also now made the Radeon HD 4850 official, including Sapphire. The 4850 is scheduled to be priced at $199 US (£100.72), while the 4870 will be priced at $299 US (£151.33).