Sapphire HD 4890 Reviewccokeman -
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The Sapphire HD 4890 is based on the same architecture as the HD 4870 but utilizes a more advanced core with better memory management to allow higher clock speeds and increased performance. The Sapphire HD 4890 goes out the door with a GPU clock speed of 850MHz with a memory speed of 975MHz. These speeds are 100MHz and 75MHz, respectively, higher than the speeds on the HD 4870. Since the HD 4890 is based on the R77 architecture it uses the same 800 processing cores and 956 million transistors. The difference in computing performance increases from 1.2TFLOPs to 1.36TFLOPs, with an increase in bandwidth from 115GB/s to 124.8GB/s.
Connectivity on the HD 4890 comes in the form of two Dual link DVI port and a single HDTV port that can be used with the dongle to convert to composite cabling. The rear of the card has an air intake for the cooling fan. Some of the cooling framework of the GPU reference cooler can be seen through this opening. The HD 4890 is CrossfireX capable with up to four cards on a supporting motherboard. The two bridge connections allow for multiple cards to be run in a CrossfireX configuration.
The Sapphire HD 4890 relies on the use of the ATI reference cooling solution to get rid of the heat the GPU and memory create under load. The fan used in this cooler is the typical squirrel cage rotary fan that is nothing short of loud at full song. The heatsink is a made up of a copper base with three heatpipes running to an aluminum fin array. The base of the copper cooler has a step on it to make sure the heatsink is in direct contact with the GPU core. The memory is cooled by a large passive heatsink that covers the GDDR5 memory, as well as the MOSFETs for the power circuit.
The Sapphire HD 4890 is built around the R790XT GPU core. This GPU is built on a 55nm process and features close to a billion transistors, 800 Unified Shader Processors running at 850MHz, 100 MHz faster than the clock speeds delivered by the HD 4870. The memory used on the Sapphire HD 4890 is 1GB of GDDR5 memory made by Quimonda and is rated for operation at 1000MHz. The memory on the HD 4890 is clocked at 975MHz and runs through a 256-bit bus. The power circuitry is located toward the back end of the PCB.
Now that we know what's under the hood, it's time to find out just how this new offering from Sapphire and ATI performs.