PowerColor Radeon X1900 GT 256MB - Page 1

by Hilbert Hagedoorn on: 06/14/2006 07:00 AM [ ] 0 comment(s)

A Guru3D fact

One MHz represents one million cycles per second. The speed of microprocessors, called the clock speed, is measured in megahertz. For example, a graphics processor that runs at 600 MHz executes 600 million cycles per second. Each computer instruction requires a fixed number of cycles, so the clock speed determines how many instructions per second that processor can execute.

Well my friends, let's get this article started, as usual .. in-depth on the architecture. The Radeon X1900 GT is of course a product of the latest X1000 family of ATI GPUs. The X1900 GT series is priced at a great 300,- USD. This new graphics card is running at a tact frequency of 575 MHz accompanied with it's memory running at (2x600MHz) 1.2 GHz. Speaking about memory, it's gDDR3 memory and there's 256MB of it.

I would not be rather shocked to see the GT work with an XT BIOS, why ? Because this is the same chip with a couple of things disabled. It looks like this products come from the same product line. So yeah .. correct .. it's the same chip yet is has less pixel pipelines and shader processors active.

Just like ATI's "concentrated" Radeon X1800 part, the X1800 GTO, the Radeon X1900 GT incorporates the full feature set of the R580 architecture. It however has one internal unit disabled. This means that the number of pixel pipelines in this part is reduced to twelve, which also leaves the core with 36 pixel shader units compared to 48 on a full Radeon X1900. Despite being effectively 'de-activated' from the pixel pipelines in this chip, the number of texture units in the X1900 GT is also reduced to twelve compared to sixteen on a full R580 core.

Cutting down the pipeline in half will have a tremendous effect on performance, something that the 36 pixel shader units will have to make up for. The number of Vertex processors remains the same though, a good eight of them are activated. So, factually seen from a lot of views .. this product is close to the X1800 GTO, yet with some more horsepower under the hood in the form of pixel processors.

The PowerColor X1900 GT is equipped with 256MB 256-bit memory. Samsung K4J55323QG GDDR3 memory rated at 1.4ns to be precise.

1000/1.4= 714 So we see that this memory can be pushed higher than it's default clocks for sure. Something good to know for our overclocking session.

Some miscellaneous features:

Ultrathreaded Architecture with fast dynamic branching
12 Pixel Shader Processors
8 Vertex Shader Processors
512-bit ring-bus memory controller
256-bit memory interface
DX9 Shader Model 3.0 support
Simultaneous support for HDR and Anti-aliasing
Avivo video & display feature set
H.264 playback acceleration
Two dual-link DVI outputs
Full 10-bit display processing & output capability
CrossFire support
Single-slot PCI Express board configuration

Radeon card	Pixel Shader Units	Vertex Shader Units	Texture Units	Core Frequency	Memory Frequency	Memory	Price in USD	Available
X1900 XTX	48	8	16	650	775	512 gDDR3	549	Now
X1900 Crossfire	48	8	16	625	725	512 gDDR3	599	Now
X1900 XT	48	8	16	625	725	512 gDDR3	479	Now
X1900 AIW	48	8	16	500	500	256 gDDR3	499	Now
X1800 XT	16	8	16	625	1.5 GHz	256/512 gDDR3	329 /449	Now
X1900 GT	12	8	16	575	1.2 GHz	256MB gDDR3	299	Now
X1800 XL	16	8	16	500	1.0 GHz	256MB gDDR3	449	Now
X1800 GTO	12	8	16	500	1.0 GHz	256MB gDDR3	249	Now
X1600 XT	12	5	4	590	1.38 GHz	128 / 256 MB	199 / 249	Now
X1600 PRO	12	5	4	500	780 MHz	128 / 256 MB	149 / 199	Now
X1300 PRO	4	2	4	600	800 MHz	256 MB	109	Now
X1300	4	2	4	450	500 MHz	128 / 256 MB	99 / 129	Now
X1300 Hypermemory	4	2	4	450	1 GHz	32 / 128 MB	79	Now

As you can see in the chart I placed the X1900 GT in a very peculiar position, this is a very oddly placed product performance wise. You'll notice that the more common games will have performance close to the X1800 GTO/XL. Rich Pixel Shaded games will benefit from the 36 pixel shader units and thus all of a sudden the card will position itself much higher in the rankings - close or even higher than a X1800 XT.

You will also notice this in our benchmark session. The product varies a great deal in terms of positioning in performance. The 12 pixel pipelines are hurting it's overall performance, something that the extra pixel shader processors have to make up for bigtime.

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