While rumors suggested that the Radeon 5700ís ďJuniperĒ graphics core could support as many as 1120 stream processors and a 192-bit memory interface, unfortunately those rumors were untrue. Instead what ATI has essentially done is much simpler than that: take a Radeon 5870, slice it in half, and youíve got a Radeon 5770. Take a 5850, slice it in half, and youíve got a Radeon 5750.
As a result, the 5770 is equipped with 800 stream processors and 128-bit GDDR5 memory interface, while the 5750 gets by with 720 stream processors and also utilizes a 128-bit GDDR5 memory interface:
|Radeon 5800 vs 5700 Series Comparison|
|ATI Radeon 5750||ATI Radeon 5770||ATI Radeon 5850||ATI Radeon 5870|
|# of Transistors||1.04 billion||1.04 billion||2.15 billion||2.15 billion|
|Die Size||166mm2||166mm2||334 mm2||334 mm2|
|# of Stream Processors||720||800||1440||1600|
|# of Texture Units||36||40||72||80|
|# of ROPs||16||16||32||32|
|Max Board Power||86W||108W||151W||188W|
|Idle Board Power||16W||18W||27W||27W|
Those of you who were hoping for more shaders and a wider memory interface are likely going to be pretty disappointed by this at first, but thanks to high clock speeds, the 5700 series cards are still able to deliver more shading and texturing horsepower than ATIís primary performance GPUs from last year, the Radeon 4850 and 4870:
|Radeon 5700 vs Radeon 4800 Comparison|
|Radeon 4770||Radeon 4850||Radeon 4870||Radeon 5750||Radeon 5770|
|# of Transistors|| 826 million||956 million||956 million||1.04 billion||1.04 billion|
|Core Clock Speed||750MHz||625MHz||750MHz||700MHz||850MHz|
|# of Stream Processors||640||800||800||720||800|
|Compute Performance||960 GFLOPS||1.0 TFLOPS||1.2 TFLOPS|| 1.008 TFLOPS||1.36 TFLOPS|
|Texture Fillrate||24 GTexels/sec||25 GTexels/sec||30 GTexels/sec||25.2 GTexels/sec||34 GTexels/sec|
|Pixel Fillrate||12 GPixels/sec||10 GPixels/sec|| 12 GPixels/sec||11.2 GPixels/sec||13.6GPixels/sec|
|Z Fillrate||48 GSamples/sec||40 GSamples/sec||48 GSamples/sec||44.8 GSamples/sec||54.4 GSamples/sec|
|Memory Clock Interface/Type||128-bit GDDR5||256-bit GDDR3||256-bit GDDR5|| 128-bit GDDR5|| 128-bit GDDR5|
|Memory Clock Speed||800MHz (3.2Gbps data rate)||1000MHz (2.0Gbps data rate)||900MHz (3.6Gbps data rate)||1150MHz (4.6Gbps data rate)||1200MHz 4.8Gbps data rate)|
|Memory Bandwidth||51.2GB/sec||64GB/sec|| 115.2 GB/sec||73.6GB/sec||76.8GB/sec|
|Max Board Power||80W||110W||160W||86W||108W|
As you can see in the chart above, ATI uses the same basic structure as RV770, with 10 SIMD cores for the 5770 and one texture unit per SIMD core. ATI disables one SIMD core for the Radeon 5750, leaving 720 active stream processors and 36 texture units.
Thanks to their high clock speeds, Radeon 5750 and 5770 compare well against the 4850 and 4870 in many aspects; the Radeon 5750 clearly outclasses the Radeon 4850 while also needing less power. The Radeon 5770 only falls short to the 4870 in memory bandwidth, where itís limited to 76.8GB/sec of peak bandwidth versus the 4870ís 115.2GB/sec. Thatís a difference of exactly 1.5X more bandwidth in favor of the Radeon 4870.
As such, the Radeon 5770 isnít going to be able to keep up with the Radeon 4870 under any moderate or high resolutions, especially if you crank up the AA, but ATIís banking on the 5770ís DX11 feature set to make up the difference.
As weíve stated previously, besides potentially delivering improved image quality, game developers can leverage DX11 to also improve performance, this could potentially be used to close part of the gap separating the 5770 from the 4870. Now obviously this wonít help the 5770 perform any better than the 4870 with todayís DX9 and DX10 games, but it could play dividends down the road as more DX11 apps appear.
The Radeon 5700 cards completely outclass ATIís previous mainstream GPU, the Radeon 4770.