Technical data / specifications

	ATI Radeon HD 4890	ATI Radeon 4870	ATI Radeon 4850
Process	55 nm	55 nm	55 nm
Transistors	956 M	956 M	956 M
GPU clock	850 MHz	750 MHz	625 MHz
Stream processors	800	800	80
Compute performance	1.36 TFLOPs	1.2 TFLOPs	1.0 TFLOPs
Texture units	40	40	40
Texture fillrate	34.0 GTextels/s	30.0 GTexels/s	25.0 GTexels/s
ROPs	16	16	16
Pixel Fillrate	13.6 GPixels/s	12.0 GPixels/s	10 GPixels/s
Z/Stencil	64	64	64
Z/Fillrate	54.4 GSamples/s	48 GSamples/s	40.0 GSamples/s
Memory type	GDDR5	GDDR5	GDDR3
Memory clock	975 MHz	900 MHz	1000 MHz
Frame buffer size	1024 MB	512 MB / 1024 MB	512 MB / 1024 MB
Memory data rate	3.9 Gbps	3.6 Gbsp	2.0 Gbps
Memory bus	256 bit	256 bit	256 bit
Memory bandwidth	124.8 GB/s	115 GB/s	64 GB/s
Maximum board power	190 W	160 W	110 W
Idle board power	60 W	90 W	30 W

With the ATI Radeon HD 4890 AMD brings in the first major overwork of the successful 4800 series. The chip also known as RV790 mainly recieved improvement regarding the clocks. Therefore the GPU now offers 850 MHz which is 100 MHz higher than the it was with the 4870. Furhter the memory does now 1950 MHz which is 150 MHz higher than it was with the predecessor.

As a by product of adjusting the GPU and memory clock frequency AMD/ATI also gets a higher memory bandwidth as well as higher pixel- and texel fillrates. Therefore they got from 10 to 13.6 GPixels/s and from 25 to 34 GTexels/s.

What they didn't touch is the manufacturing process, the number of transistors, die stream processors, the number of texture units and the ROPs. This lets us conclude that there were no bigger changes to the core design itself.

Obviously increasing the clock rates and not transisting to a smaller manufacturing process goes hand in hand with an increase in dissipation power. With 190 watts the ATI Radeon HD 4890 needs 30 watts mor than its predecessor 4870. But on the other side it is remarkable that the idle power is a third lower than with the 4870. This will result from lower idle frequnecies when the card is in 2D mode. Therfore it successfully sets the engine clock to only 240 MHz.



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