AMD Radeon HD 4800 Series

Say hello to the Radeon HD 4850 and Radeon HD 4870. We think you will be pleasantly surprised with the real-world gaming experiences we are having with AMD’s new GPUs. We evaluate the Sapphire Radeon HD 4870 and VisionTek Radeon HD 4850.

Introduction

Today we cover AMDآ’s new Radeon HD 4870 and Radeon HD 4850. Compared to previous Radeon GPUs, the 4800 series GPUs have been improved in every way.

We know most of you just care about the gaming performance so we are going to be to the point on specifications to give you the information you need to know so you can hurry up and start gaming!

Radeon HD 4800 Series

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AMD is taking on a new strategy with video cards. They want to give you the آ“perfect gaming solution for $200-$300.آ” That is certainly an admirable goal. We know that NVIDIAآ’s GeForce GTX 280 offers a great gameplay experience, but it also costs over $600. AMDآ’s strategy is a scalable one; think smaller GPUs in parallel. In fact, the new ATI Radeon HD 4800 series GPUs are only 16mm across versus NVIDIAآ’s 24mm across on its GTX 200 series GPU. The Radeon HD 4800 series GPUs are indeed small; they are literally the size of a dime.

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AMD has made significant improvements in the architecture, in every component. The AMD ATI Radeon HD 4800 series is based on a 55nm process with 956 Million transistors. They have bumped the stream processor count up to 800 (versus 320 on the HD 3000 series.) They have also bumped up the texture units to 40 from 16 in the last generation. However, the ROP count stays the same at 16, though there have been improvements made to the ROPs to increase performance. Before anyone asks, yes, they have fixed the AA performance.

The stream processors have undergone many changes; they are now laid out as 10 SIMD cores, each with 80 32-bit stream processors (800 total). They also now can do fast double precision processing with integer big shift operations for all units. There are 80 scalar stream processors per unit with 16KB of local data cache that is shared. Each unit has its own control logic and each has 4 dedicated texture units plus L1 cache. Tessellation performance has also been improved. Of course, DX 10.1 is supported as well.

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The texture units have also received quite a bit of work; there is double the texture cache bandwidth of the HD 3000 series. The entire cache system has been reworked to improve performance. The ROPs have also been improved to allow better AA performance among other things. There is also a new AA mode being introduced called CFAA which stands for Custom Filter AA. There will be a drop down box in the control panel where you can select the option called آ“Edge Detectآ” which will enable the CFAA modes. آ“Box Filterآ” is the regular AA modes.

The way CFAA works is really rather simple, it uses the stream processors to do edge detect AA to provide better AA image quality, up to the equivalent of 24X AA. The great thing about it is that it does not use or need a larger memory footprint for doing this as it does not tax the framebuffer. It does however tax the stream processors, so in shader intensive games it may not be possible unless you have cycles to spare. In the games we are testing today we did not find it playable in any of them with the highest playable settings. We will be doing further investigating of performance and image quality of CFAA modes in a later evaluation and dive into more detail then.

There have also been other various improvements, such as memory controller optimizations to support the new GDDR5 memory modules. GDDR5 offers double the bandwidth of GDDR3/4 basically, and allows AMD to achieve high bandwidth on a 256-bit memory bus.

Radeon HD 4870

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The Radeon HD 4870 is AMDآ’s current high-end video card, with an MSRP of $299. For $299 you get a video card that is clocked at 750MHz core, 900MHz memory but using GDDR5 so the memory frequency is double that of double data rate, so it would be 3.6GHz. At 3.6GHz this gives you a memory bandwidth of 115GB/sec. There will be 512MB of this on board standard, though expect some add-in-board manufactures to offer 1GB models, as well as OC models. The Radeon HD 4870 has 800 stream processors, supports DX 10.1, is a dual-slot video card and rated at 160W maximum board power. It also requires only two 6-pin power connectors, no 8-pin required.

Radeon HD 4850

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The great thing about the Radeon HD 4850 is that it is only a lower clocked and lesser memory version of the Radeon HD 4870. It still contains the full 800 stream processors and 40 texture units. The core frequency is reduced to 625MHz, and instead of GDDR5 it uses GDDR3, but still 512MB of it. The memory frequency is set at roughly 2GHz, providing 64GB/sec of memory bandwidth. The other great thing about this video card is that it is priced at $199, and you should surely see that price fall in time. The Radeon HD 4850 is a single slot video card and requires only one 6-pin power connector and is rated at 110W maximum board power. Both video cards support CrossFireX fully.