Radeon X1800 GTO preview

Posted by Hilbert Hagedoorn on: 03/09/2006 08:00 AM [ 0 comment(s) ]

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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.

Hey ... you made it to the second page .. welcome .. welcome..

The Radeon X1800 GTO my friends is of course a side-product of the latest X1000 family of ATI GPUs. It's targeted at the mid-range section and offers performance very similar to that 199 USD GeForce 7600 GT. The X1800 GTO however is slightly higher priced at 249,- but is it worth the extra 50 bucks ? We'll definitely show you in today's article.

Right then, the X1800 GTO core you'll find on this new graphics card is running at a tact frequency of 500 MHz accompanied with it's memory running at (2x500MHz) 1 GHz. Speaking about memory, it's gDDR3 memory and there's 256MB of it. Do you recognize the X1800 XT specifications already? More importantly .. do you recognize the X1800 XL already ?

I would not be surprised to see the GTO work with an XL BIOS. But I'm sure a couple of buyers will definitely try that out. It looks like this products comes from the same product line. So yeah .. correct .. it's the same chip yet is has less pixel pipelines active. Now the memory frequency is definitely slower clocked compared to the 7600 GT but there's one very distinct difference .. this is 256-bit memory which efcectively can double bandwidth again. Much like that 7600 GT this graphics core is also based on a 12 pixel pipeline architecture. It has no less than eight Vertex processors and furthermore utilizes the entire feature set that the entire X1000 family of products entail.

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 acceleratio
Two dual-link DVI outputs
Full 10-bit display processing & output capability
CrossFire support
Single-slot PCI Express board configuration

Since this is card number eight that I tested in the past 48 hours I am going to save me some time by doing a little copy and paste from the X1000 article when it comes to features regarding SM3.0, AVIVO and the funky looking ringbus memory controller.

One of the hotty new ATI features is of course Crossfire. Crossfire allows you the ability (with the proper mainboard) to hook up another X1800 Crossfire edition graphics card into your PS and double up performance. At the moment we are working on an Express 3200 review in combo with the new X1900 XT Crossfire edition graphics card from ASUS .. so keep your eyes open for that one pretty soon. Let's have an overview of the ATI product lineup and it's updated prices !

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
X1800 XL	16	8	16	500	1.0 GHz	256 MB gDDR3	449	Now
X1800 GTO	12	8	16	500	1.0 GHz	256 MB gDDR3	249	Late March 06
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

Alright, let me commence the usual blurbs. The GTO of course has super support for Shader Model 3.0 as it finally became important in the industry and we now see broad support for it.

What is a shader ?

What do we need to render a three dimensional object; 2D on your monitor? We start off by building some sort of structure that has a surface, that surface is being built from triangles and why triangles? They are quick to calculate. How's each triangle being processed? Each triangle has to be transformed according to its relative position and orientation to the viewer. Each of the three vertices the triangle is made up of is transformed to its proper view space position. The next step is to light the triangle by taking the transformed vertices and applying a lighting calculation for every light defined in the scene. At last the triangle needs to be projected to the screen in order to rasterize it. During rasterization the triangle will be shaded and textured.

Graphic processors like the GeForce and Radeon series are able to perform a certain amount of these tasks. The first generation was able to draw shaded and textured triangles in hardware. The CPU still had the burden to feed the graphics processor with transformed and lit vertices, triangle gradients for shading and texturing, etc. Integrating the triangle setup into the chip logic was the next step and finally even transformation and lighting (TnL) was possible in hardware, reducing the CPU load considerably. The big disadvantage was that a game programmer had no direct (i.e. program driven) control over transformation, lighting and pixel rendering because all the calculation models were fixed on the chip. And now we finally get to the stage where we can explain Shaders. Vertex and Pixel shaders allow developers to code customized transformation and lighting calculations as well as pixel coloring functionality. Each shader is basically nothing more than a relatively small program executed on the graphics processor to control either vertex or pixel processing.

SM3 allows the programmer to fire off some very nice shader programs that in certain cases can speed up your game. The world has moved on to SM3, people expect it to be integrated and so it has and had to be been done.

Very good integration I might add because SM3 seems to work pretty darn efficiently for ATI, it has to do with dynamic branching, that matter is too complicated to explain for this article. What you need to know is that it works really well. More efficiency, that really is what the new card is all about. I'll be using that word in this review a lot. According to the chip designers every transistor in that core is constantly put to use to push the results onto your screen, yes efficiency.

Another feature in the X1000 feature, and yeah it's not new to our ears at all, yet it had a little upgrade has to do with texture compression capabilities. Almost any, well any, graphics card nowadays makes use of texture compression technology. It's been discussed here on more then one occasion, I'm sure you recognize terms like S3TC and DXTC. Basically you reduce the byte-size of a texture while maintaining the best quality as possible. However, compression equals artifacts and thus image degradation at some point.

3Dc is a compression technology designed to bring out fine details in games while minimizing memory usage. It's the first compression technique optimized to work with normal maps, which allow fine per-pixel control over how light reflects from a textured surface. With up to 4:1 compression possible, this means game designers can now include up to 4x the detail without changing the amount of graphics memory required and without impacting performance.

3Dc was upgraded a little and on the X1000 series of cards we now have 3Dc+ available to us. Let me just get it out of the way and move on. High quality normal map compression can (and could) be handled up to a 4:1 ratio and works on any two-channel texture format.

This updated + edition adds support for single-channel textures with 2:1 compression, which is good enough for stuff like luminance maps, shadow maps, HDR textures and more.

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