RADEON X1000 Memory Controller

Transcription

1 RADEON X1000 Memory Controller

2 Ring Bus Memory Controller Supports today s fastest graphics memory devices GDDR3, 48+ GB/sec 512-bit Ring Bus Simplifies layout and enables extreme memory clock scaling New Cache Design Fully Associative for more optimal performance Improved Hyper Z Better compression and hidden surface removal Programmable Arbitration Logic Maximizes memory efficiency Can be upgraded via software

3 Radeon X1800 Ring Bus Two internal 256-bit rings Run in opposite directions to minimize latency Return requested data to clients Memory writes use crossbar switch Circle around the periphery of the chip Reduces routing complexity Permits higher clock speeds One ring stop per pair of memory s Linked directly to memory interface Ring Stop Ring Stop Memory Controller Ring Stop Read Path Write Path Ring Stop

4 Programmable Arbitration Logic Prioritizes memory access requests Predicts impact of each request on overall performance Uses feedback system to maximize memory and GPU efficiency Programmable parameters Can be tuned via driver updates

5 Memory Channels Memory Devices Radeon X1800 8x s Memory Controller 256 bit interface Radeon X bit 64-bit Memory Devices 64-bit 64-bit 4x64-bit s Memory Controller

6 Cache Design Fully Associative Caches Cache lines can map to any location in external memory Earlier designs used Direct Mapped & N-Way Associative Caches Could only access limited blocks of external memory Direct Mapped Cache Graphics Memory Cache Texture, Color, Z & Stencil caches are all now fully associative Reduces memory bandwidth requirements Minimizes cache contention stalls Optimized game performance Fully Associative Cache Graphics Memory Cache Gains up to 25% clock for clock in fill/bandwidth bound cases

7 Cache Performance X1800 Z Cache Misses Relative to X % 110% 100% 90% Cache Misses 80% 70% Battlefield 2 Far Cry 3DMark05 GT1 X850 Baseline 60% 50% 40% 0% 10% 20% 30% 40% 50% 60% 70% 80% 90% 100% Demo Progress(Frames)

8 Cache Performance X1800 Texture Cache Misses Relative to X % 110% 100% 90% Cache Misses 80% 70% Battlefield 2 Far Cry HL2: Lost Coast X850 Baseline 60% 50% 40% 0% 10% 20% 30% 40% 50% 60% 70% 80% 90% 100% Demo Progress(Frames)

9 Hyper Z Improved Hierarchical Z Buffer Detects and discards hidden pixels before shading Important in scenes with heavy overdraw (i.e. overlapping objects) New technique uses floating point for improved precision Catches up to 60% more hidden pixels than X Improved Z Compression Z Buffer data is typically the largest user of memory bandwidth Bandwidth can be reduced by up to 8:1 using lossless compression New method achieves higher compression ratios more often

10 Memory Controller Performance New technology benefits most apparent in most bandwidth-demanding situations High resolutions (1600x1200 and up) Anti-Aliasing (4x and 6x modes, Adaptive AA) Anisotropic Filtering (8x and 16x Quality AF modes) Frame rates over 2x faster than previous generation in these cases

11 Anti-Aliasing Performance 100% 90% 80% 70% 60% 50% 40% 30% 20% 10% Far Cry - Regulator 0% 1600x x1200 (4XAA) 1600x1200 (6XAA) Radeon X1800 XT Radeon X850 XT Geforce 7800GTX GeForce 6800 Ultra

12 Anti-Aliasing Performance 100% 90% 80% 70% 60% 50% 40% 30% 20% 10% Battlefield 2 0% 1600x x1200 (4XAA) 1600x1200 (6XAA) Radeon X1800 XT Radeon X850 XT GeForce 7800 GTX GeForce 6800 Ultra