The Table Tells AllATI's Radeon HD 4770 becomes the standard-bearer in the $99 (£85) space. Based on established Radeon 4K-series technology it mixes in some old with new. Cutting right to the chase, a table will help explain the new GPU's architecture.
|Graphics cards||ATI Radeon HD 4770||ATI Radeon HD 4670||ATI Radeon HD 4830||ATI Radeon HD 4850||NVIDIA GeForce 9800 GT||NVIDIA GeForce 9600 GT|
|Die size||172mm²||146mm²||255mm²||255mm²||230mm² (55nm)||240mm² (65nm)|
|Memory clock (effective)||3,200MHz||2,000MHz||1,800MHz||1,986MHz||1,800MHz||1.800MHz|
|Memory interface and size (usual)||128-bit, 512MB, GDDR5
||128-bit, 512MB, GDDR3||256-bit, 512MB, GDDR3||256-bit, 512MB, GDDR3||256-bit, 512MB, GDDR3||256-bit, 512MB, GDDR3|
|DirectX/ Shader Model||DX10.1, 4.1||DX10.1, 4.1||DX10.1, 4.1||DX10.1, 4.1||DX10, 4.0||DX10.0, 4.0|
|Vertex, fragment, geometry shading (shared)||640 FP32 scalar ALUs, MADD dual-issue||320 FP32 scalar ALUs, MADD dual-issue||640 FP32 scalar ALUs, MADD dual-issue||800 FP32 scalar ALUs, MADD dual-issue||112 FP32 scalar ALUs, MADD dual-issue + MUL (unified)||64 FP32 scalar ALUs, MADD dual-issue + MUL (unified)|
|Multi-GPU||CrossFire - four-board||CrossFire - four-board||CrossFire - four-board||CrossFire - four-board||SLI - three-board||SLI - two-board|
|Hardware-assisted video-decoding engine||AMD UVD 2 - full H.264 and VC-1 decode, plus dual-stream decode||NVIDIA's PureVideo HD - full H.264 decode and partial VC-1 decode, plus dual-stream decode|
|Current etail price||£85 (estimated)||£57||£75||£110
40nm manufacturing process
By dint of its nomenclature, the Radeon HD 4770 should slot in-between the HD 4670 and HD 4830/4850 GPUs, but it's not as simple as that in performance terms. ATI's keen to cut costs but still retail a potent architecture, so the HD 4770 is the first consumer card to be based on a 40nm manufacturing process. The benefits to ATI are clear, as it can ship considerably more GPUs on to a given-sized wafer than if fabricating them on the established 55nm process, and the estimated die-size of 172mm² is significantly smaller than the Radeon HD 4830/4850's.
We see the 40nm move as a dip in the water for upcoming high-end GPUs, so don't be surprised to see the next iteration of ATI hardware - RV8xx - baked on the same process.
Half-node 40nm also marks the first time that GPUs have been manufactured on a smaller process than CPUs, which are at 45nm right now. It shows that the evolution of the GPU has been forced at a faster pace than their CPU counterparts, if nothing else.
Shaders and clocks
Look a little further down the table and you'll see that the GPU ships with 640 steam processors that operate at 750MHz. Therefore it beats out a Radeon HD 4830 on pure GLOPS throughput through higher clock-speed, but gives way, just, to the 800SP HD 4850. Agnostic to the shaders, fillrate is the highest of all the cards in the line-up.
Radeon HD 4750
ATI will add to the HD 47x0 brand with the release of a slower-clocked card to be known as Radeon HD 4750. Sharing the same architecture traits as its bigger brother we reckon it will debut for around £75.