New RV570 GPU

The top of the X1950 Pro card

Bottom of the card

Rather than procuring the services of R580 once again to service the mainstream segment, ATI’s come up with a brand new GPU to power the Radeon X1950 Pro: RV570.

In order to make their newest mainstream GPU more cost effective to produce, ATI’s enlisted the help of their manufacturing partner TSMC. To cut production costs, ATI’s decided to go with a smaller manufacturing process, 80-nm for RV570 versus the 90-nm process that was used previously in R580.

Another difference between the RV570 GPU that is used in the Radeon X1950 Pro in comparison to the R580 chip that was used previously for Radeon X1900 GT is that RV570 is built from the ground up with 36 pixel shaders.

On paper the R580 GPU used previously in the Radeon X1900 GT also had 36 pixel shaders, but its GPU actually physically contained 48 pixel shading units. ATI merely disabled 12 of the shaders for X1900 GT. This means at the chip level, the X1900 GT costs just as much for ATI to produce as the X1900 XTX/X1950 XTX. With 36 shaders from the start, RV570 contains fewer transistors than R580: approximately 330 million in RV570 versus the 384 million found in R580.

With fewer pixel shaders, and its new 80-nm manufacturing process, RV570 is a smaller chip than R580. RV570 boasts a die size of approximately 230.5 square mm, in comparison R580 is 315 square mm. Thanks to its smaller die size, RV570 is much cheaper for ATI to produce than R580, as they yield more RV570 chips per silicon wafer.

RV570 has one other key addition over previous ATI GPUs: integrated CrossFire built-in.

The X1950 Pro is similar in length to the X1900 GT

The X1950 Pro is actually a mm or so longer than the X1900 XTX

Previously ATI had relied on a small array of external chips to power their CrossFire technology used on CrossFire master cards like the Radeon X1900 XT CrossFire. A Xilinx Spartan XC3S400 FPGA chip was used to handle the compositing duties for CrossFire, while TMDS receivers from Silicon Image were used to receive data from the slave Radeon graphics card. Now all of these duties have been integrated into RV570 itself, so a custom CrossFire card isn’t necessary: all Radeon X1950 Pro cards already have the technology built into the GPU.

Sitting at the top left corner of every Radeon X1950 Pro card are two 12-bit CrossFire connectors. When two Radeon X1950 Pro cards are connected together for CrossFire, software automatically assigns one board as the master board, and the second card as slave. According to ATI, the two 12-bit connectors deliver 24-bit performance at screen resolutions as high as 2560x2048 at 60Hz, making it ready for 30” displays like the Dell 3007 WFP.

X1950 Pros running connected for CrossFire!

New CrossFire cable is similar to the SLI ribbon cable

We’ll be discussing ATI’s X1950 CrossFire solution in much more depth in tomorrow’s X1950 Pro CrossFire Performance article.

Clock speeds

ATI clocks the RV570 chip found in the Radeon X1950 Pro at the same speed as the Radeon X1900 GT: 575MHz. The memory subsystem does see a slight boost however, as the X1950 Pro’s memory runs at 690MHz (1.38GHz effective), that’s 90MHz higher than the X1900 GT’s 600MHz memory. The X1950 Pro sports the same 256-bit memory interface first introduced with the R520 last year. If you recall, ATI uses 8 32-bit memory controllers on R520/R580, and now RV570, that’s twice the number of memory controllers as competing GPUs from NVIDIA. With more controllers onboard, ATI’s GPUs can serve more read/write requests simultaneously and thus operate more efficiently. ATI’s 512-bit ring bus memory architecture also carries over intact on RV570.

The following chart summarizes how ATI’s newest RV570 GPU stacks up to previous ATI offerings and the NVIDIA GeForce 7900 GS it competes with:

ATI/NVIDIA GPU Comparison
	GPU	Die Size	Core Clocks	Pixel Shaders	Vertex Shaders	ROPs	Texel Fill-rate (Mtexels/sec)	Memory Speed	Memory Bandwidth	Price
Radeon X1900 XT 256MB	R580	315	625	48	8	16	10000	1450	46.4	$250
Radeon X1950 Pro	RV570	230.5	575	36	8	12	6900	1380	44.2	$199
Radeon X1900 GT	R580	315	575	36	8	12	6900	1200	38.4	$195
Radeon X1800 GTO	R520	264	500	12	8	12	6000	1000	32	EOL
GeForce 7900 GS	G71	196	450	20	7	16	9000	1320	42.2	$199