X-bit labs

NVIDIA GeForce2 GTS Preview

Category: Video

by FastSite

[ 04/26/2000 | 12:00 AM ]

Well, today, on 26 April 2000, NVIDIA Company announced its new sixth generation graphics processor called GeForce2GTS. Some time ago this GPU was also known as NV15.

Table of contents:

• Conclusions
  

Well, today, on 26 April 2000, NVIDIA Company announced its new sixth generation graphics processor called GeForce2 GTS.Some time ago this GPU was also known as NV15.

If you have been with us all the time, you probably remember that we posted the first details on NV15 in January already.You may take a look at our NV15 Early Preview if you like, you will simply make sure that we never told you any nonsense. Moreover,we almost guessed the official name of a new NVIDIA GPU. Nevertheless, the name also includes a three-letter abbreviation -GTS, which means GigaTexel Shading. It was not for nothing that they chose this particular name, because it signals thatNVIDIA's newcomer features superb performance and is equipped with an integrated NVIDIA Shading Rasterizer (NSR).

Here is a list of GeForce2 GTS key features:

• 256bit graphics core made of two 128bit units
• 0.18 micron technology
• 200MHz graphics core working frequency
• 4 rendering pipelines, with 2 texturing blocks each
• Up to 200MHz memory bus working frequency, for now only 166MHz (333MHz final frequency) DDR SGRAM will be used
• The supported memory types include: DDR SGRAM and a standard SDR SDRAM/SGRAM
• 8-128MB local graphics memory
• 5.3GB/sec memory bus bandwidth (the peak is achieved at 166MHz DDR memory working frequency)
• Pixel fillrate: 800 million pixels per second
• Texel fillrate:
• 1 texel per 1 pixel: 800 million texels per second
• 2 texels per 1 pixel: 1600 million texels per second
• 350MHz RAMDAC
• Max display resolution - 2048x1536 at 75Hz
• TMDS transmitter integrated into the chip supports digital monitors and resolutions up to 1600x1200
• External bus interface: full AGP 4x/2x (including SBA, DME and Fast Writes) and PCI 2.2 (including Bus Mastering).AGP 4x Fast writes allows direct data transfer between CPU and GPU at up to 1GB/sec avoiding the PC system memory.It should undoubtedly have positive influence on the general performance and help to somehow reduce the system memorybus utilization. We wish there were normal Fast Writes support in the drivers finally.

3D Graphics:

• Geometric engine GeForce2 GTS: hardware Transformation and Lighting, clipping (deletion of all the scene detailsbeyond the end frame)
• HW T&L capacity (peak): 25 million textured polygons per second
• 8 source hardware lighting for the whole scene
• Full OpenGL and DX7 support - Transform and Lighting, Cube environment mapping, projective textures and texturecompression
• NSR engine provides Pixel Shaders hardware support via D3D8
• Supports Full-Scene Hardware Anti-Aliasing (HW FSAA)
• Supports hardware effects, such as: Motion Blur, Depth of Field via D3D8
• Full support of DXTC and S3TC via DX and OpenGL correspondingly
• Hardware vertex blending with 2 skinning matrices, which is quite enough in most cases
• Rendering in 16 and 32bit color depth mode
• Hardware bump mapping support. Embossing, Dot Product3, EMBM (finally!)
• Supports the textures up to 2048x2048 @ 32bit
• Programmable texture blending modes
• 8-bit stencil buffer
• 16/24/32bit Z-buffer
• Fully-fledged support of hardware acceleration OpenGL 1.2 for OS Linux

Video

• Supports hardware decoding of all HDTV formats
• Supports all ATSC resolutions including 1080i
• 8bit alpha-blending for video and graphics (can be used for subtitles or animated menus)
• supports VIP 2.0 level I port (8bit, 75MHz), which allows connecting external MPEG2 encoders/decoders
• Second generation Motion Compensation
• Requires a TV encoder for TV output, and GeForce2 GTS chip already has the digital interface for these encoders

The scheme below will give you a general idea of GeForce2 GTS architecture:

As you can easily notice, GeForce2 GTS has a new integrated High-Definition Digital Video Processor (HDVP), which allowsplaying the video in any of the today's formats, and an integrated TMDS transmitter, which allows connecting monitors to thedigital interface. Moreover, the performance of all the main units of the new GPU has been significantly increased comparedto GeForce 256. In this respect, we have every reason to suppose that this time the use of more than one light source, suchas Directional Light, won't tell that greatly on the overall performance.

Moreover, they added an NSR unit to the rastering engine. We will come back to it a bit later in our preview.

To get a better idea of GeForce2 GTS compared to its predecessor GeForce 256, we suggest taking a look at the table below:

We would like to particularly stress one of the key features of GeForce2 GTS - two texturing blocks on each of the fourpixel pipelines. With this peculiarity we get the so called "free" multitexturing, which means that the fillrate doesn'tdrop when two textures are applied over one pixel. Besides, it appears possible to arrange hardware anisotropic filteringbased on 16 texture samples. This should undoubtedly have a highly positive effect on 3D graphics quality compared toGeForce 256.

And now let's particularly dwell on NSR (NVIDIA Shading Rasterizer).

NSR is a separate unit, which work is very closely connected with that of the texturing blocks. To make our explanationsound a bit more illustrative let us compare NSR with a certain "layer" between the texturing blocks, which blends texturesfollowing some scheme and at the same time implements multitexturing effects. Here is an example of a simple scheme:

(TB1@TB2)@TB3

where:

• TB = texturing block, handles one texture
• @ - blending operation. Before, these operations were predefined, and now they can be programmed by game developers.

Going into details, we can say that multitexturing effect is created in the following way: we take two textures and blendthem according to a certain scheme (an ordinary diffuse lightmap, for instance, is just multiplication (*), while specularlightmap - is addition (+)). The final result is then blended with a next texture on another scheme, etc. According toDirect3D 8.0 specification, there can be up to 8 textures blended. In fact, this is still an unattainable top, becausethe number of textures, which can be involved to create multitexture effect equals to the number of parallel texturingblocks forming one texel. GeForce 256 allows involving two texturing blocks to form one texel (which means that onlytwo textures can be blended), while GeForce2 GTS features four texturing blocks available for one texel forming (whichmeans that four-texture blending is possible). However, this operation can be arranged in a bit different way. Forexample, GeForce 256 supports two textures, but at the same time allows 8 effect stages and hence for the remainingstages it can use "non-texture" values, such as vertex interpolated color, t-factor, etc.

So, the primary innovation provided in NSR is the opportunity for game developers to program their own multitexturingeffects with the help of new schemes.

Of course, multitexturing effects are not a novelty to us, they were available before NSR as well. That's why if wedisregard marketing tricks, NSR will turn out not a totally new unit, but an older unit provided with new additionalfeatures. All multitexturing effects are implemented on the pixel level and the programming of new multitexturingeffects is supported in a new API D3D8 from Microsoft included into DirectX 8.0 (not announced officially yet).

They introduced a new term in Direct3D 8.0 - Pixel Shader. This is exactly the tool, which allows carrying outunified operations over the pixels, i.e. it is a programming mechanism for multitexturing effects used together withthe predefined effects. In fact, Pixel Shader is an API for NSR.

For multitexturing effects all the calculations are made for each single pixel covered by a polygon. Pixel operationstake place in case of programmable multitexturing effects as well as in case of predefined effects. So, the results obtainedare highly precise and hence no artifacts spoil the picture.

Actually, Pixel Shader is a universal programmable replacement for DX7 "texture stage state", i.e. Pixel Shader is amethod of developing multitexturing effects "manually". Some time ago texture blending was allowed only according tocertain previously defined schemes (as a rule they included one or two operations, such as adding two arguments and thensubtracting their product from the sum). But now Pixel Shader serves as a manually defined "program" of textures blending.With Pixel Shader you can create your own effect with the help of elementary operations (it includes the following operations:+, -, /, * and a couple of other more exotic ones; all of them can be combined). Especially for this purpose Microsoftdevelopers worked out a certain pseudo-assembler, which was intended to help in multitexture effects programming. Itincludes the following notions:

• Registers
• Instructions
• Texture Address Operations (e.g., Perturbations)
• Instructions modifiers
• Instruction arguments modifiers

So, from now on, only the programmer's imagination can limit the realization of multitexture effects: game developers cannow freely create their own multitexture effect independently of the initially available set. Note that with the predefinedschemes everything will work faster than with the programmed ones. This performance difference results from the fact thatprogrammed schemes use a general purpose pipeline instead of a specially optimized one.

We should also point out that Pixel Shader doesn't require any specific hardware. The only must is the possibility oftexturing blocks external programming.

In fact, Pixel Shader is a serious change of the entire multitexturing concept. The major drawback of this innovationis the necessity for game developers to design a multitexturing unit anew. By the way, Pixel Shader allows creating veryexact shadows but unfortunately you won't be able to eliminate sharp borders. Moreover, Pixel Shader can save you sometexture memory in a certain situation. And one more thing: the so long awaited EMBM is none other but an elementaryoperation from the point of view of Pixel Shader (there is a special command for that).

Besides external programming of multitexture effects, NSR also allows parallel implementation of seven differentpredefined pixel operations:

• Base Texture
• Per-Pixel Bump Mapping
• Per-Pixel Diffuse Lighting
• Per-Pixel Specular Lighting
• Colored Fog
• Ambient Light
• Alpha Transparency

Each of the seven operations is a single pass operation, which prevents significant performance drops. These seven operationsare carried out over four pixels in parallel due to four pixel rendering pipelines of GeForce2 GTS.

Despite a rather skeptical attitude of some game developers towards the mere idea of Pixel Shaders, the outcome is reallyworth it. You can see a few examples of Pixel Shader for various effects below:

Composite Pixel Effects		Per-Pixel Bump-map
Per-Pixel Light

As you can clearly see from the pictures, special effects applied on the pixel level provide higher realism of the imageswhen modeling various textures or physical phenomena. Geforce2 GTS has hardware Pixel Shader. On all the other cards, whichcan't boast the same hardware support, this effects can be programmed and implemented with the help of the CPU.

GeForce2 TGS has an integrated HDTV processor decoding all 18 ATSC formats including 720p and 1080i. The integratedTMDS transmitter allows connecting displays directly to the digital interface without any additional controllers. So,the graphics cards on GeForce2 GTS can turn out a universal multimedia machine, if any of the graphics cards manufacturerswill ever design them. The picture below shows the possible applications of the graphics card on GeForce2 GTS as a multimediacenter:

As we have expected GeForce2 GTS boasts a much better playback of different video formats compared to GPU GeForce 256.Take a look at the table:

Together with the launching of GeForce2 GTS, eight companies are going to announce their manufacturing of graphicscards on it. They are: Acer Group, MSI, ASUS, Gigabyte, Leadtek, Elsa, Creative and Guillemot. And some PC manufacturers,such as Dell, Compaq, HP, Micron, Quantex and Gateway, are planning to start using GeForce2 GTS based graphics cards inthe systems. The first graphics cards on this chip by Creative are expected to appear in the US in the end of Aprilalready. However, there won't be many of them at first and they will sell at $349 for a 32MB DDR SGRAM version equippedwith a TV-out. Quite expensive, of course, but since there are simply no real competitors, this is pretty logical.Nevertheless, if ATI starts supplying its graphics cards on RADEON 256 a bit later in summer, GeForce2 GTS cards willundoubtedly get cheaper.

Some game developers are going to release special game levels, which could demonstrate the power of GeForce2 GTS. Forexample, id Software will introduce a new Quake3 Arena level (see a screenshot on the right), and WXP will offer you another"Isle of Morg" demo based on Experience gaming engine (see a screenshot on the left).

As for the performance of GeForce2 GTS based graphics cards, everything is quite predictable here and the benchmarks results,which have already penetrated into the web, prove that the performance gain in real games will be about 25-30% at higher resolutionscompared to GeForce 256. It is achieved due to higher Pixel Fillrate by GeForce2 GTS. However, these numbers are valid only forthe games without HW T&L. On the other hand, you can count the games using the power of HW T&L to the full extent on the fingersof your hand. Nevertheless, we are promised about 30 games with a fully fledged HW T&L support by the end of the year 2000.Time will show.

Conclusions

NVIDIA Company once again proved the world that they are the first in technology as well as in marketing. New productsfrom NVIDIA come out regularly and enter the market without any displeasing delays. NVIDIA's competitors have a goodexample to follow.

In terms of technology NVIDIA is also ahead of the entire gaming industry, having integrated an NSR engine into itsnew GPU. In the meanwhile, DirectX 8.0, which will support Pixel Shader, is expected only in August. That is why thefirst games with programmable pixel multitexture effects will appear only by the end of the year.

By that time, NVIDIA is planning to announce another GPU aka NV20. However, this doesn't mean that GeForce2 GTSwon't be demanded. Besides NSR support, a new NVIDIA GPU features cool performance of both: rastering engine (800million pixels fillrate) and geometric unit (25 million polygons). Add here perfect video format decoding andplayback unit, and you will get a clear picture of a leading product.

In the near future we are planning to share our personal experience about GeForce2 GTS with you, guys, that'swhy don't go too far away from your PCs :)