NEC PowerVR PCX
The PowerVR PCX series from NEC is a family of 3D graphics chips for the PCI bus that are based on the IP of the PowerVR Series 1 and are thus tilebased deferred renderers (TBDR). The PowerVR PCX series was developed in collaboration with VideoLogic .
Versions
PowerVR PCX1
The NEC PowerVR PCX1 was the very first graphics chip with PowerVR technology (Series 1) and came onto the market in October 1996 as a 3D add -on card at about the same time as the Voodoo Graphics chip from 3dfx . The chip was developed and produced by NEC . The chip was roughly on par with the Voodoo 1, but had severe problems in Direct3D due to the lack of a Z-buffer due to the architecture and could not prevail against the Voodoo 1. In addition, the manufacturer's own PowerSGL interface, unlike 3dfx ' Glide, could not prevail.
As a specialty it should be noted that this PowerVR series uses its RAM exclusively for textures. The cards did not have a VGA output, but instead wrote the 3D scenes directly into the RAM of the main graphics card via the PCI bus. Their memory was therefore also used and its timing influenced the speed. Its size also determined the possible resolutions, with the PCX cards providing playable up to 1024 × 768 - in 1996 a unique selling point that has existed for years. Finally, the main card determined the signal quality of the image, in contrast to the voodoo process in which it was the 3D card.
The PCX1 was the first PC graphics processor to use the "Infinite Planes" method, a bandwidth-saving procedure by only calculating the non-covered 3D objects in a scene. In doing so, he laid the foundation for a special characteristic of the PowerVR graphics series , tilebased deferred rendering (TBDR). Only then was it possible for the chip to achieve a speed comparable to that of the 3dfx Voodoo 1 (64-bit memory connection) despite its very narrow 32-bit memory connection .
Nevertheless, this chip was also probably the first 3D chip that attracted attention with possible tricks for achieving high 3D benchmark values. For this purpose, the driver recognized the D3D test from Microsoft and calculated it less precisely, but much faster. It wasn't until years later that something similar became known with nVidia GPUs ( see ).
A well-known graphics card with this chip was the VideoLogic Apocalypse 3D.
PowerVR PCX2
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In August 1997 , NEC then added the PowerVR PCX2 , which contained some detail improvements such as bilinear filtering and floating point formatting compared to the PCX1. This improved the image quality and the processor was relieved. Nevertheless, this chip only caught up with Voodoo Graphics-based accelerators with Pentium II processors. The reason was in its architecture.
Like all chips of this time, both PCXs have to adapt the Direct3D commands in the driver to their internal rendering unit, but one that is fundamentally different here due to the lack of the Z buffer. Only the Nvidia Riva had already been designed in hardware for Direct3D, which was a reaction to its predecessor architecture, which was completely incompatible with it . The conversion is a processor task due to the system. Thus, the computational effort in PowerVR systems was higher than in the competition. In addition, there was the additional effort of dividing the scenery into the eponymous tiles. It was not until the PowerVR Series 2 that this tiling was adopted by the processor, along with the management of the polygons contained (in a "display list").
Once created, the tiles are sent individually to the chip, which frees it from the invisible polygons in a 12 kilobyte cache. From this ISP (Image Synthesis Processor) the image tile now moves to the TSP (Texture and Shading Processor) in the same housing, which draws and illuminates the surfaces of the remaining polygons. To do this, it combines the key data from its 4 KB parameter cache with the textures in the card memory and writes the result to the frame buffer of the main graphics card. This saves the Z-buffer in the chip-external memory as well as multiple accesses to it, as well as the provision and processing of ultimately hidden textures. First, however, the enormous bandwidth advantage was exchanged for a strong processor reference as soon as a game did not offer PowerSGL support.
With its architecture, 3Dfx was very close to the also very promising OpenGL standard at the time , which was superior to the still very new DirectX in terms of maturity and functionality. This proximity minimized the effort for a translation program ( MiniGL wrapper ) for 3Dfx . This converts the most important OpenGL commands of the application into data compatible with the chip according to the scheme of the Direct3D driver. 3Dfx was based on the scope of the instruction set required by the game Quake (this also led to the name "QuakeGL"). In order to achieve comparable performance values with its MiniGL wrapper in the architecture that is once again remote from OpenGL, the PowerVR driver temporarily discarded all lighting effects.
Similar to the competitor at the time, 3dfx Voodoo Rush , a combined 2D / 3D card, the Videologic Apocalypse 5D, also appeared with the PCX2. Here, too, a supplier chip was used due to a lack of 2D expertise. This turned Tseng Labs first with the ET-6000 and later his successor ET 6100th Since 2D and 3D chips used different types of memory, this increased the number of components used - the resulting price contributed to the lack of market success. In order to compensate for this system-related disadvantage, a "Sonic" version was later released with the addition of an ESS Maestro 1 sound chip.
Unlike the Voodoo Rush, these cards had no performance disadvantages compared to the pure 3D version due to their separate image memory.
The only add-on 3D cards with this chip were the VideoLogic Apocalypse 3D x and the Matrox m3D.
Based added on this chip Video Logic (now renamed Imagination Technologies) is a four-time texture compression, increasing together with NEC the clock to 100 MHz at 250 nm feature size to the graphics chip PowerVR2DC (CLX2) for the Sega Dreamcast , NAOMI and Naomi 2 to deliver . Its PC version NEC Neon 250 was not released until the end of 1999, but with a 25 MHz higher clock rate.
Model data
| Model | Launch |
Code name |
Manufacturing process |
Transis- interfere in millions |
cutting stelle |
Max. Memory in MB |
Clock (chip) in MHz |
Clock (memory) in MHz |
Render Pipes x TMU x VPU |
Fill rate in MT / s |
Memory bandwidth in GB / s |
Storage type |
Memory bus width |
DirectX / OpenGL version |
Features |
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| PowerVR PCX1 | 1996 | Midas 4 | 0.5 µm | 0.6 | PCI | 4th | 60 | 60 | 1x1 × 0 | up to 60 | 0.24 | SDRAM | 32 bit | 3 / - (MiniGL wrapper) |
TBDR , PowerSGL, RenderWare |
| PowerVR PCX2 | 1997 | Midas 5 | 0.35 µm | 1.2 | 4th | 66 | 66 | to 66 | 0.26 |
- The fill rate depends on the processor and main graphics card.
See also
Web links
Individual evidence
- ↑ mdgx.com Microsoft D3DTest
- ↑ heise.de Apocalypse 3D - 3D benchmark trick
- ↑ pure.com Improvements to the PCX2
- ↑ geocities.com ( Memento from January 25, 2008 in the Internet Archive )
- ↑ wave-report.com Polygon setup and tiling migrate from the processor to the graphics chip in the second series
- ↑ stason.org PCX1 specifications
- ↑ tomshardware.com
- ↑ the-nextlevel.com PowerVR2DC
- ↑ Code names according to PowerVR ( page no longer available , search in web archives ) Info: The link was automatically marked as defective. Please check the link according to the instructions and then remove this notice.
