- Highly optimised rendering technique improves performance without the need for expensive components.
- No hardware geometry acceleration
- 4X AGP mode not supported.
Although the 3D graphics accelerator market is increasingly dominated by nVidia, a few competitors remain willing (and able) to challenge the market leader. An alternative to nVidia's GeForce range is the new Kyro II chipset, designed by Imagination Technologies (previously VideoLogic) and manufactured by STMicroelectronics. The Kyro II is a PowerVR chip, similar to that used in Sega's ill-fated Dreamcast console. However, it's a second-generation 0.18 micron part with enough power to give nVidia's mainstream GeForce MX chipset a run for its money, and it's this chip that drives the new £111 (ex. VAT, £129.99 inc. VAT) Hercules 3D Prophet 4500.
Finished in Hercules' trademark blue and bearing the same chunky heatsink as the 3D Prophet II Ultra, the 3D Prophet 4500 certainly looks the part. As you might expect from a company renowned for performance products, Hercules has moved away from the typical 32MB board design and fitted the 3D Prophet 4500 with 64MB (the maximum amount supported by the Kyro II).
Like previous PowerVR chipsets, it's the way that the Kyro II rewrites the rules of the 3D rendering process that gives it an edge over more traditional hardware. Most graphics chips render a scene in full -- complete with textures and geometry -- before removing (culling) the objects that are hidden behind others. In a complex 3D scene, this means that a great deal of processing time and bandwidth is taken up with creating objects that aren't even visible in the final render.
Thanks to the Kyro II chipset, the 3D Prophet 4500 avoids this unnecessary work by breaking the scene into 32 by 16 pixel 'tiles' -- which are small enough to be held in the chip's buffer without loading them into RAM -- and running Hidden Surface Removal (HSR) routines to eliminate 'invisible' geometry. Any textures that would have been processed and applied to these culled objects are also discarded before they are passed across the card's 128-bit bus, significantly reducing the workload and bandwidth required.
Tile-based rendering and HSR allows a graphics card whose chipset and RAM are both clocked at a relatively low 175MHz to compete against products with faster specifications on paper. Not only that, but the Kyro II can also push enough pixels to make full-scene anti-aliasing (FSAA) a possibility. As you can see from our benchmark results, the 3D Prophet 4500 may not come close to matching the GeForce3's outstanding FSAA performance, but it can still manage a playable 60-plus frames per second until you switch to the demanding four-samples-per-pixel technique.
What of the Kyro II's drawbacks? Although you get hardware motion compensation for DVD movie playback, the Kyro II lacks any kind of geometry acceleration (T&L) -- in contrast to both nVidia's GeForce and ATi's Radeon chipsets. At 270MHz, the DAC seems a little under-specified against the more commonplace 350MHz. And, while you can fit it in a 4X AGP system, the Kyro II only supports 2X mode.
That said, the 3D Prophet 4500 performs pretty impressively for the price (which is £20 less than Hercules' 64MB GeForce2 MX board), and would make a good choice for a mid-range PC.