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Radeon HD 4870: Better Than GTX 260!

Radeon HD 4870: What’s Improved?

GPUHD 4850HD 4870GTX 260GTX 280
GPU frequency625 MHz750 MHz576 MHz602 MHz
ALU frequency625 MHz750 MHz1242 MHz1296 MHz
Memory frequency1000 MHz900 MHz999 MHz1107 MHz
Memory bus width256 bits256 bits448 bits512 bits
Memory quantity512 MB512 MB896 MB1024 MB
Number of ALUs800800192240
Number of texture units40406480
Number of ROPs16162832
Shading power1 TFlops1.2 TFlops715 GFlops933 GFlops
Memory bandwidth64 GB/s115.2 GB/s111.9 GB/s141.7 GB/s
Number of transistors956 million956 million1400 million1400 million
Engraving process0.055µ0.055µ0.065µ0.065µ
Die surface area260 mm²260 mm²576 mm²576 mm²
Shader Model supported4.

The difference between the Radeon HD 4870 and its little brother the 4850 can be summed up in two characteristics: theoretical power, increased by 20% solely via higher clock speeds (the number of ALUs remain unchanged, unlike Nvidia’s approach), and above all memory bandwidth, which has almost doubled (+ 80%). This change is the result, as we’ve seen, of the use of GDDR5, with an equivalent frequency that’s nearly doubled compared to the GDDR3 used on the Radeon HD 4850. This type of memory is expensive, but less so than using a 512-bit or at least a 448-bit bus, which would have been necessary to achieve an equivalent bandwidth using GDDR3 memory as Nvidia has chosen to do — not to mention higher power consumption (memory chips + controller). The result is that the Radeon HD 4870’s bandwidth is similar (in fact 3% higher) to the GeForce GTX 260’s.

By the way, the theoretical superiority of the 4870’s raw processing power over the GTX 260’s is particularly impressive considering that the 4870’s GPU has a die surface area that’s barely 45% of the Nvidia card’s!

On the other hand, we can’t help but mention the obvious limitation that emerges from a reading of these specs – the memory quantity, still limited to 512 MB on the 4870. That’s only slightly over half as much as the GTX 260, and even when you consider that the Radeon cards suffer much less than the GeForce ones when using central memory in cases of frame buffer limitations, we’ll need to keep a close eye on how performance and rankings evolve as resolution increases. Also note that certain manufacturers, such as PowerColor, have already announced 1-GB versions of the Radeon HD 4870, but they won’t be available to do that before the end of July.