Now, we called the Cyprus chip modest but once you start looking at its stats you realise that word does it rather a disservice. Thanks to its 40nm manufacturing process, AMD has managed to pack 2.15billion transistors into a piece of silicon that’s just 334mm^2. In contrast, the previous top dog, the GT200b that powered the GTX285 had 1.4billion transistors packed into a 490mm^2 die.
Now, if you’re unfamiliar with the inner workings of AMD’s latest cards then you might like to read our review of the HD 4870 to catch up with the core features then come back and join us for this review.
With the RV870, AMD has essentially taken the basic inner workings of RV770 (HD 4870) and doubled a load of it up. Most notably the number of SIMDs has been doubled from 10 to 20. This in turn doubles the number of stream processors from 800 to 1,600 and the texture units from 40 to 80. Meanwhile the number of ROPs has also doubled from 16 to 32. All this lot will be running at 850MHz – the same as the HD 4890.
What hasn’t changed is the amount of memory each card will use and the interface that the chip uses to talk to it, namely you’ll get 1GB of GDDR5 memory running at 4.8GHz communicating over a 256-bit interface making for a total bandwidth of 154.6GB/s.
There will also be an HD 4850 card based on the RV870 chip. However, this will have two of the SIMDs disabled and will run at lower clock speeds. This will result in it having 1,440 stream processors, 72 texture units, a core clock speed of 725MHz, and memory running at 4GHz. The number of ROPs, amount of memory, and the memory bus width remain the same though.
While there aren’t a huge number of feature changes in this card that are relevant to the scope of this review there are, well, a few. The first is the reintroduction of supersampling anti-aliasing (AA) support. This is a brute force alternative to the much more common place multi-sampling AA. It results in much better image quality but has a massive impact on performance, thus it having fallen out of favour.
Another image quality improvement with the HD 5870 is better anisotropic-filtering, which is now completely angle independent. This means that no matter what angle you’re looking at a surface in a 3D scene you’ll get the same level of image quality improvements.
The final under-the-skin change to the HD 5870 is support for Dolby TrueHD and DTS-HD Master Audio bit-streaming through the card’s DVI and HDMI video outputs. As with previous cards, the HD 5870 enables you to use a single cable from your computer to pass video and audio through an HDMI cable (using a DVI-to-HDMI adapter in the case of the DVI outputs) to your TV. However, whereas previous cards didn’t support all possible streams, with the addition of these formats, this card now supports all major digital audio streams used in DVDs and Blu-rays.